BimmerFest BMW Forum banner

Detailed step by step diagnostic DIY ... dead battery ... parasitic current drain

116K views 105 replies 18 participants last post by  S62M5 
#1 · (Edited)
PLEASE IMPROVE THE STEPS BELOW SO ALL BENEFIT!
(Advice is always welcome!)

EDIT: Updated as per Fudman to pull the FSU rather than fuse F76.
EDIT: Updated as per 540iman that the nature of the current draw implicates certain circuits.
EDIT: Updated as per edjack in that the four doors must be shut in order for the computers to go to sleep.The last few days, twice now, I go out to the bimmer, and, ... well ... nothing.
---

No click. No lights. No horn. No nuthin'.
At first, I thought I had left the lights on or maybe I had charged too much portable electronics - but I wouldn't have done that twice.

So as to add value with every repair, here's my story, as it unfolds (so that others can follow suit in the future).

History
:
a) I had put in a new (acm Germany) FSU in, oh, about three years ago (need to check) <=== here's the thread ... 2/2/2009
b) I had put in a rebuilt (Bosch 120A) alternator & belt drive system a couple of years ago (need to check) <=== here's the thread 7/26/2010
c) I had put in a new (Duralast 49DL) battery just over a year ago (need to check) <=== here's the thread ... 9/19/2011

Definition:
Active period: The first 16 minutes after you exit the vehicle, shut all doors, and then open the trunk (as evidenced by the indicator light by the shift lever being lit).
Quiescent period: After 16 minutes, the computers shut down, and that orange indicator light by the shift lever goes off.
Note: Most say you should see something like 30 ma quiescent draw AFTER the car shuts down at 16 minutes (but I'm seeing 80 milliamps on my 2002 525i).

Flowchart: (thanks to Fudman & 540iman for updating the overall procedure)
Step 1: Disconnect & charge the battery (I use a 4 amp charger - I wish I had a 6 amp charger though)
Step 2: Drive to Autozone (or equivalent) to have the charging system tested (or test it yourself with a DMM, using this procedure).
Step 3: If it passes step 2, then measure parasitic drain (active & quiescent) with and without the FSU in series with the negative battery terminal
Step 4a: If you find double-digit current draw, then pull the FSU, and check current draw again (both active & quiescent)
Step 4b: If you find single-digit current draw, then pull fuse F56, and check current draw again (both active & quiescent)
Step 4c: If if it's neither of those culprits, then start pulling all 88 fuses, one by one, with an ammeter in series with the battery
Note: You 'can' pull the 40A yellow blower circuit fuse F76 for step 4a - but for reasons Fudman explains, it's better to pull the FSU instead.

DIY Procedure:
0. Print the fuse lists from EF1 to EF5, and from F1 to F114 for each of the six fuse panels (see detailed fuse listing below)
1. For obvious reasons, keep your ignition key somewhere safe OUTSIDE the vehicle (e.g., in the trunk lock or in your pocket)
2. Open the trunk and leave it open; shut all four doors; & lock the vehicle using the key fob (taking note of the orange light near the shift lever)
3a. With a 10mm socket on a 6-inch extension, remove the battery negative cable
3b. Optional: Discharge stored charge in the electronics by temporarily disconnecting BOTH battery cables, and shorting the two CABLES with a wrench (do not short the battery terminals!)
3c. Reconnect the battery positive cable if you performed optional step 3b above.
4a. Set your ammeter to the 20 amp or 10 amp range (whichever you have that is highest)
4b. Hook the positive (red) lead to the brown negative battery cable (use a clamp or alligator clips to attach)
4c. Hook the negative (black) lead of the ammeter to the bare negative battery post (I used a heavy gauge wire with large alligator clips on each end to attach)
5. Work the meter range down from amps to milliamps (you must be ready for up to 20 amps - but you want to see something around 2 amps active to less than 100 ma quiescent)
6. With the ammeter still connected, wait for shut down (about 16 minutes) as indicated by the automatic transmission console light going off
Note: Some DMMs shut off automatically about 10 or 15 minutes into your test, so you'll need to activate those DMMs periodically.
7. Make a note of the TOTAL current drain after shutdown (all lights should be off)
8a. If current drain is around 2 amps active and less than 100 ma quiescent, then you're probably OK
8b. If current drain fluctuates in the teens at any time (active or quiescent), then pull the FSU & retest
8c. If current drain is in the single amps (quiescent period), then pull fuse F56 & retest
9. If neither the FSU nor fuse F56 make a difference and your current draw is still greater than about 100ma quiescent, then it's time to debug by pulling the fuses, one by one
10. Disconnect your ammeter, re-connect the battery, again wait for shutdown - and then, one by one, pull the 88 fuses, putting your ammeter leads across the open contacts
Note: Unfortunately, some fuses, when pulled, will wake the car up and force you to wait anywhere from 1 minute to the full 16 minutes to continue
11. You can either remove and immediately replace each fuse, or, you can successively remove all fuses sequentially (starting with the lowest amperages first)
12. Write down the parasitic drain for each fuse & troubleshoot the circuit with the highest parasitic drain.
Unfortunately, my Fluke 75 requires me to move the leads to go from the 10Amp range down to the 300ma range (which resets the car!).
Note: You can measure total parasitic drain in series with the battery, or individually, across each fuse's terminals.

For the record, this is what the battery charger did last night & this morning:
 

Attachments

See less See more
2
#3 · (Edited)
It could be, as you suggest - as I don't know WHAT the problem is just yet - but - I know what to do (which is my homework).

O'Reillys said the battery & alternator were OK. Here's a picture of the O'Reillys tool in action today ...


Then I took it to Autozone, where the battery & alternator tested good a second time (showing 14.13 volts at idle):


So, now it's time to check the FSU out, even though it was replaced in 2009 (I haven't noticed any blower fan problems ... but that's the next thing I'll do).

Doing my homework, I find these quotes scattered about the forum, which relate to unplugging the FSU fuses:

That's a single, square socket housing for two large fuses, F75 & F76, unlike the individual socket arrangements shown in the attached photos. And yeah .... it's hard to get your hand up in there (be sure to disconnect the battery first), let alone finagle the fuses upward and out with your fingers. Be sure to put the right fuse back into the right slot, too. Easily interchangeable.....
BEHIND GLOVEBOX (look from underneath):
F75 = 50A, Auxiliary fan (some say it's red)
F76 = 40A, Heater blower (some say it's yellow) [cn90 says it should have 12V when HVAC is turned on]
Pull the bottom plastic panel off that is under the glove box, pull it straight back toward the seat.
Then unhook the side supports for the glove box.
This is what your will see.


To access F75 and F76 ... close the glove box and behind the glove box is a plastic panel with a hole in it (the panel is directly behind the glove box) Pull it towards you. Takes a bit of a nudge.
Then there are all kinds of wires bound together and various connectors that if you pull out will probably incapacitate the car -- who knows. I had to contort myself to lay on my back and look up in the well on the passenger side.
Yes, the two large fuses -- 75 and 76 are in the middle of this mess, and yes, it is a tight fit (took forever to locate them with the little flash light; some say they are obvious but they weren't to me; of course, now I know exactly where to look). God knows how one gets them in. To get the fuses out, I had to nudge the first fuse on each side -- couple of sparks -- God knows what those shorts did -- and finally it came out -- the fan stopped.
1. Car dies periodically (and blower has wierdities at the same time)
2. Unplug FSU ...
3. If intermittent battery death stops, then you've pinpointed the problem
4. Replace FSU
If it's not the FSU, then I'll need to go, one by one, down all 88 fuse slots (F1 to F114).
Here is what I think each pin does:
#1 = ground
#2 = 12V power, 40 amp fused
#3 = input to fsu from heat/ac module
#4 = output power to the blower motor? (speed 1?)
#5 = output power to the blower motor (speed 2?)

And, here is what I measured between each pin and ground (the FSU body):
#1: Old FSU = 600Kohms, new FSU = 11.2 ohms
#2: Old FSU = 3.02Mohms, new FSU = 1.22Mohms
#3: Old FSU = 2.22Mohms, new FSU = 608Kohms
#4: Old FSU = 2.14Mohms, new FSU = 602Kohms
#5: Old FSU = 3.05Mohms, new FSU = 1.28Mohms
Code:
NOTE: For the wiring diagram below:
F76 - Fuse 76 (yellow, 40 amps, under glovebox and above GM3 connector X254).
15 - Ignition power (RUN & START)
30 - Batt positive (+)
31 - Batt negative/gnd (-)
[/quote]


Elvis, this is a fantastic writeup and saved me money and grief. I have a couple of comments:

1. BLOWER STOPS WORKING COMPLETELY. This repair also works in at least some cases when the blower STOPS WORKING ALTOGETHER. A lot of the web-based commentary seems to imply that the FSU replacement only fixes blowers that are intermittent, or that have speed problems. In my case, the blower stopped working at EVERY SPEED. It was just like it was switched off. I followed all the commentary and tested it at all speeds -- NOTHING!! I was really afraid then, that the blower motor was kaput, and not the FSU, based on all the comments. But I decided to try the FSU first, and I'm glad I did. For $52 bucks, free shipping from autohausaz, it was really worth a try.

2. CONTORTION. For me to do this repair, I had to lower the passenger seat down as low as it would go, and move it as far back as possible, into an almost bed-like position. Then I climbed into the seat backwards, with my feet toward the back of the car, my body upside down, so I could get my head and arms underneath the dash, facing up towards the FSU. It's very close in there, but even a monstrously large person like myself (6'2", 280 lbs) managed to get in there with some difficulty. If you have a small, thin person in your family who is very flexible, you may want to engage them for the removal and installation of the FSU.

3. FUSES. Of course, the first thought is to check the fuses. Once the "easy" ones in the glovebox are checked and found to be ok, the thought is that Fuse 75 or 76 might be to blame. They are big 50 amp fuses that are located in a very difficult place, behind the glovebox. I know there is a lot of commentary out there about how to remove them. But REPLACING them is something else altogether. No one mentions that there is an aluminum brace that is in the way. After diddling around for a long time, I found that the only way to REPLACE those fuses is to jam your hand in back of the aluminum brace by force, and punch the fuses in from the top. The aluminum brace will move enough to let you get your big fat hand back in there if you use force. Of course, in my case, all of this was wasted, since the fuse was not the problem. However, to get to the FSU, it really helps to have the glovebox out of the way anyway, so all the effort was not wasted.

4. FSU REPLACEMENT. Make a mental note of the orientation of the FSU as you take it out. There is little space to work down there, and it is very difficult to keep turning the new one around trying to fit it back in. Plus the new one is not exactly the same shape as the old one. I printed out a picture of the FSU in place from Elvis' DIY and brought it with me out to the car. That really helped. Nevertheless, be prepared for some jockeying to get the old FSU out, and the new FSU in -- the only thing that I was concerned about was damaging the very soft prongs in the new one while installing. Luckily that turned out to be not a problem.

5. SOFT PRONGS. I should note that the new part, from BEHR (the old one was made by VALEO) had very soft prongs. The old one's prongs were very hard and could not be bent, but the new ones were very bendable. In fact, I thnk I accidentally bent them a little while fooling with it. I did not know whether this made a difference, but where they touched each other, I bent them back so that they did not touch, and were aligned in neat rows. Maybe this made no difference, but I didn't want to take the chance.

In my case, as soon as I replaced the FSU, everything went back to normal! It's like magic. I was dreading having to disassemble half the car and replace the blower motor -- but that won't be necessary, thanks to our friend Elvis! Really appreciate what you have done here for all of us.

--Ron
 

Attachments

#4 · (Edited)
PRINT this list of fuses and write down the parasitic draw for each while debugging

We should all add value before, during, and after every repair, so here's my homework assignment, so far on the 88 discrete fuse spots (not all of which have fuses in them).

(Note that F1 to F5 exist in two different locations, just to confuse you, so I'll refer to the ebox ones as EF1 to EF5, and the glovebox ones as F1-F5).

There are SIX fuse box locations in my 2002 BMW 525i E39 (here is a 1997 540i fuse location chart):

  • EF1 to EF5 <= at the back of the ebox under the passenger side cabin air filter housing (5 fuse spots)
  • F1 to F45 <= in the glove compartment top panel (45 fuse spots)
  • F46 to F66 <= directly above the battery (21 fuse spots)
  • F67 to F74 <= don't exist
  • F75 to F76 <= behind the glove compartment (2 fuse spots)
  • F77 to F99 <= don't exist
  • F100 to F106 <= above the battery positive terminal (7 fuse spots)
  • F107 to F114 <= under passenger side front seat carpet (8 fuse spots
IN THE White E-BOX UNDER PASSENGER SIDE CABIN AIR FILTER:
EF1 = 30A, MAF, Cam sensor #1, DME, T-Stat, Evap emission valve (some say it's 30A - DME, Injectors, SMG Hydraulic unit)
EF2 = 30A, Fuel injectors, Both Vanos solenoids, Cam sensor #2, SAS pump electrical valve (some say it's 30A - DME, Idle control valve, Fuel tank ventilation valve, Fuel pump)
EF3 = 20A, Cam sensors, MAF, Crank Sensor, Heated O2 sensors (some say it's 30A, others say 25A - E-box fan, Transmission RPM sensor, CPS, MAF sensor, Fuel pump relay, SAP relay, A/C Compressor relay, Fuel tank leakage diagnostic module, SMG selector lever)
EF4 = 30A, DME (some say it's 30A - Oxygen sensors and oxygen sensor heater circuits)
EF5 = 30A, Unloader relay, power to coils (some say it's 30A - Fuel injector relay)

Note: Photo courtesy of JimLev.

---
IN THE ROOF PANEL OF THE GLOVEBOX:
F1 = 30A, Windscreen wiper
F2 = 30A, Headlight cleaning system, Windscreen washer system
F3 = 15A, Horn
F4 = 20A, Passenger comp/trunk lighting, Windscreen washer system
F5 = 20A, Sliding tilt/roof
F6 = 30A, Outside mirror adjustment, Central locking system, Window lift
F7 = 30A, Cigarette lighter
F8 = 25A, ABS/ASC Control Module (Note: F8 was empty in my 2002 525i)
F9 = 15A, Air conditioner, Heated washer jets [JimLev says it handles the heated washer jets and the Check Control Module panel]
F10 = 30A, Passenger seat adjustment
F11 = 7.5A, Servotronic
F12 = 5A, Immobilizer
F13 = 30A, Driver seat adjustment, Steering column adjustment [JimLev says F13 goes to all of the motors in the drivers seat and the two steering column adjuster motors in a left hand drive gas engine E39 built after 9/'99] [cn90 shows an F13 trick here]
F14 = 5A, Engine control
F15 = 7.5A, Diagnosis plug, Engine control (JimLev adds: Oil level sensor, Data connector under the hood next to the ABS module (no data conn after ~6/2000), Alternator, Temp switch in DME box for cooling fan in bottom of DME box, Range switch for automatic tranny)
F16 = 5A, Light module
F17 = 10A, ABS, Automatic stability control
F18 = 5A, Instrument cluster
F19 = 5A, (empty) Electronic damper control [QSilver7 says F19 is in-between the ignition switch and an unloader relay terminal 15]
F20 = 7.5A, Air conditioner, Heated rear window, Heater, Tyre pressure control system [JimLev says F20 and F105 power relay K201, which itself gets power from F75]
F21 = 5A, Anti-glare inside mirror, Driver seat adjustment, Garage door opener [JimLev says F21 also powers the current cutoff relay, garage door opener, rear view mirror, park distance control module, and the cig lighter relay]
F22 = 25A, Fuel pump
F23 = 7.5A, (empty in my 2002 525i) Heater, Rear centre arm rest
F24 = 5A, Instrument cluster, Shifting gate illumination, Tyre pressure control system
F25 = 7.5A, Multi-information display, Radio
F26 = 5A, Wiper Relay I & Wiper Relay II (Note: F26 was empty in my 2002 525i)
F27 = 30A, Central locking system, Window lift
F28 = 15A, (empty in my 2002 525i) Transmission control, diesel
F29 = 30A, Central locking system, Outside mirror adjustment, Window lift
F30 = 25A, ABS
F31 = 10A, ABS, Automatic stability control, Fuel pump
F32 = 25A, Active seat, Electric seat heating, Roller sun blind
F33 = Open (empty in my 2002 525i)
F34 = 10A, Heated steering wheel (empty)
F35 = 5A,(empty in my 2002 525i) Rear A/C blower
F36 = Open (empty in my 2002 525i)
F37 = 5A, Immobilizer
F38 = 5A, Horn, Shifting gate illumination
F39 = 7.5A, Charging socket, Courtesy mirror illumination
F40 = 5A, Airbag, Instrument cluster
F41 = 5A, Brake light, Light module
F42 = 5A, Airbag
F43 = 5A, (Telephone), (On-board monitor), Radio, (Rear Washer) (Rear washer pump)
F44 = 5A, Multi-function steering wheel, MID, Radio, (Telephone)
F45 = 7.5A, Roller sun blind


IN TRUNK BATTERY COMPARTMENT:
F46 = 15A, Blower relay/Parked Car ventilation/Receiever, parked car ventilation (Note: F46 was empty in my 2002 525i)
F47 = 20A,(empty in my 2002 525i) Additional heater, independent heater
F48 = 5A, Anti-theft alarm system [Note: The alarm will sound if/when you pull this fuse]
F49 = 30A, (empty in my 2002 525i) Air suspension
F50 = 7.5A, (empty in my 2002 525i) Air suspension
F51 = 30A, (empty in my 2002 525i) Rear cigarette lighter
F52 = 30A, (empty in my 2002 525i) Cigarette lighter (AUS)
F53 = 7.5A, Central locking system [fuel door solenoid issue, which disables the central locking system] [JimLev adds Rear lid motor relay K70, Central locking & fuel door relay K121, Window motor relay K90, Diversity amp or antenna amp]
F54 = 25A, (empty) M5 Fuel pump
F55 = 20A, (empty) Rear washer, Rear washer pump
F56 = 30A, (On-board monitor), (CD changer), Radio, (Navigation system) [Black540eye adds On-board Monitor, Radio, Video Module, CD Changer, Amplifier, GPS Control Module, GPS Receiver]
F57 = 10A, (Telephone)
F58 = 10A, (On-board monitor), (Telephone), Radio, (Navigation system)
F59 = 20A, (empty) Trailer socket
F60 = 50A, (empty) Elecronic damper control
F61 = 5A,Park distance control module/ Seat heater switch, left rear/ Seat heater switch. right rear (empty in my 2002 525i)
F62 = Open (empty in my 2002 525i)
F63 = 7.5A, Radio relay/ Loud alarm relay/ Transparency relay/ Alarm control unit (empty in my 2002 525i)
F64 = 30A, On-board monitor/ Radio CD changer/ Amplifier/ GPS receiver (empty in my 2002 525i)
F65 = 10A, Transceiver (empty in my 2002 525i)
F66 = 40A, heated rear window


THESE DO NOT EXIST:
F67 = (does not exist in the E39)
F68 = (does not exist in the E39)
F69 = (does not exist in the E39)
F70 = (does not exist in the E39)
F71 = (does not exist in the E39)
F72 = (does not exist in the E39)
F73 = (does not exist in the E39)
F74 = (does not exist in the E39)

BEHIND GLOVEBOX (look from underneath):
F75 = 50A, Auxiliary fan (red) [QSilver7 says the aux fan is the electric fan in front of the radiator which also goes on when the AC is initiated.]
F76 = 40A, Heater blower (yellow) [cn90 says it should have 12V when HVAC is turned on][QSilver7 says the heater blower controls the air velocity for the cabin/interior HVAC system.]

Neither of these huge fuses is easy to remove or put back (due to the cramped location), but luckily the yellow one is the one aft, which is easier than the red to remove.


THESE DO NOT EXIST:
F77 = (does not exist in the E39)
F78 = (does not exist in the E39)
F79 = (does not exist in the E39)
F80 = (does not exist in the E39)
F81 = (does not exist in the E39)
F82 = (does not exist in the E39)
F83 = (does not exist in the E39)
F84 = (does not exist in the E39)
F85 = (does not exist in the E39)
F86 = (does not exist in the E39)
F87 = (does not exist in the E39)
F88 = (does not exist in the E39)
F89 = (does not exist in the E39)
F90 = (does not exist in the E39)
F91 = (does not exist in the E39)
F92 = (does not exist in the E39)
F93 = (does not exist in the E39)
F94 = (does not exist in the E39)
F95 = (does not exist in the E39)
F96 = (does not exist in the E39)
F97 = (does not exist in the E39)
F98 = (does not exist in the E39)
F99 = (does not exist in the E39)

ABOVE BATTERY POSITIVE TERMINAL:
F100 = 200A, Fuse panel 4, F107-F114
F101 = 80A, Power supply for fuses F46-F50 and F66
F102 = 80A, Power supply for fuses F51-F55 [wiring diagram here]
F103 = 50A, Open
F104 = 50A, Unloader relay terminal 15
F105 = ?A [JimLev says F20 and F105 power relay K201, which itself gets power from F75]
F106 = 100A, F75, Engine cooling fan relay stage 3


UNDER PASSENGER SEAT: (see more details in this thread & this thread)
F107 = 50A, SAS airpump Special Fuse: BMW PN 6113836590
F108 = ??A, [QSilver7 says this is for the ABS/DSC control unit]
F109 = ??A, [QSilver7 says this is for the DME (motor electronics)]
F110 = 80A, Power supply F1-F12 and F22-F26
F111 = 50A, Data link connector/ Ignition switch
F112 = 80A, Light control module
F113 = 80A, Power supply F13 and F27-F30/ Light Module
F114 = 50A, Data link connector/ Ignition switch
 

Attachments

#5 · (Edited)
I ran into a dastardly problem in that I can't switch meter ranges without waking up the car (because I have to disconnect & reconnect the test leads), so I can't get better granularity than that below without adding a jumper (which I don't have so I'd need to make out of heavy wire & clamps).

But, given these results ...

How do these numbers look for initial "active" (first 16 minutes) and, then, later "quiescent" (after 16 minutes) parasitic drain?

  • First 16 minutes: Active current = 2.31 amps
  • After 16 minutes: Quiescent current = 90 milliamps

 

Attachments

#6 ·
I'd recommend modifying a fuse so that you can measure the current through each circuit. A lot easier and saves a lot of running to the trunk. This is what I did.

to do this break the fuse material, then solder a wire to each term on the outside of the fuse. You can then connect multimeter to the fuse and measure current through the circuit.
 
#8 · (Edited)
PS 90ma is a little on high side but not that it should cause a problem. I believe it should be around 45ma.
I wish I had done the parasitic drain test when things were working OK, so that I'd know what the nominal quiescent values are for my bimmer - because 90ma seems about double what it should be - but - as noted, it's not all that bad.

The good news is that I think I'm getting closer to the culprit. The problem appears to be intermittent, so the longer I spend diagnosing, the more I am learning.

For example, see this 30-second video taken a little while ago when I returned from an errand and started checking the parasitic drain again.
All of a sudden, the active current began fluctuating between 2.27 amps and 11.53 amps!
http://youtu.be/RzVRU69xa0A

Here are those same clicking sounds, about every 3 seconds, taken from the cockpit just after the video above (they seem to be coming from behind the MID but I can't really be sure).
http://youtu.be/bbvm6scUui0

Notice the audible clicks coming from the front of the car, behind the dash somewhere, where each time you hear a click, the quiescent current jumps from about 2.27 amps to about 11.53 amps!

In that 30-second video, the current fluctuates at about 3 second intervals from:

  1. 2.27 amps
  2. 11.53 amps
  3. 2.27 amps
  4. 11.18 amps
  5. 2.27 amps
  6. 11.35 amps
  7. 2.27 amps
  8. 11.10 amps
The fluctuating current is different depending on whether the bimmer is in the initial active phase (first 16 minutes) or in the quiescent (computers off) phase (after 16 minutes); but here are two back-to-back photos taken of the current fluctuation when the clicks were heard:
Note: I was getting worried about my 10 amp meter because the current was as high as 14 amps during these regular click cycles.


To further debug:

  • I moved the passenger seat aft & lowered the back as far as it would go
  • I disconnected the battery (so that sparks wouldn't fly)
  • I removed the underglovebox panel (breaking the white tabs in the process)
  • I located the FSU in the tunnel but decided to remove the fuse instead since I have never done that before.
Here is a picture of the FSU in situ:

Then:

  • I desperately tried to disconnect the three harness connectors in the way
  • These diabolical things could foil Houdini!
  • How on earth does that big one disconnect?
    (If we could disconnect it - we'd have an easier time with the two fuses!)


Since I couldn't remove the three harness connectors for the life of me:

  • I pushed up the closest (furthest aft) F76 yellow fuse with a screwdriver

And, then I reconnected the battery to test for parasitic drain.

Guess what?

  • First 16 minutes: Active current = 1.89 amps
  • After 16 minutes: Quiescent current = 80 milliamps


In summary, the parasitic current data is hugely inconsistent depending on whether the "clicking" sound is heard.

However, I'm pretty sure the intermittent huge fluctuating parasitic current is due to the ACM FSU I bought in 2/2/2009 going bad.
With the fuse F76 removed, I'll keep an eye on the parasitics for a few days - but the evidence seems to implicate the aftermarket ACM FSU.

Meanwhile, since I KNOW it will be difficult to get F76 back in, does anyone know HOW to get those three harness connectors off (especially the largest one, which would make access muuuuch easier when removed)?
The connector seemed similar to that of the ABS control module connector, in that there is a u-shaped slider - but I could only move it so much - and then nothing else moved.

A video of someone smart enough to remove that connector would be a blessing to see!
 

Attachments

#9 ·
heres how to unlock those connectors
http://www.bmwgm5.com/GM3_E39_Removal.htm

I too am having the same issue. Not my fsu, just replaced. Battery is new though drained. Im thinking its fuse 4 or 9. Cant tell yet more trouble shooting to go. I get the clicky noise too even after fsu. I've read that perhaps the heater valve is the cause of the clicks. One of those fuses I think 4 controls that. Look forward to updates.
 
#10 ·
heres how to unlock those connectors
http://www.bmwgm5.com/GM3_E39_Removal.htm
Ah! Fantastic description! Thanks for finding that.

It looks like I had already tried the right moves, but, I just didn't force it hard enough.
1. The large connector, as the description says, starts out easily - but then jams tight. It seems I need to use more force.
2. The two smaller connectors have that locking tab; I guess I just have to press down on that locking tab with more force, and then swing the lever to the left (in the picture).


Those instructions you found make it seem intuitively easy! :)


This closeup of the GM Module board from your reference shows the tabs that need to be overcome:


Im thinking its fuse 4 or 9
Those two should be relatively easy to pull since they're both in the glovebox:
F4 = 20A, Passenger comp/trunk lighting, Windscreen washer system
F9 = 15A, Air conditioner, Heated washer jets [Check Control Module panel]

I get the clicky noise too even after fsu. I've read that perhaps the heater valve is the cause of the clicks
The clicks 'do' sound weird. Nothing I've ever heard before, at least not when the car is just sitting there, doing nothing (except clicking & sourcing current). I'm lucky I caught it on video as it didn't happen all the time. The noise actually sounds like a relay kicking on and off - but I have no idea what relay that could be.

I admit, it was almost dark by the time I pulled the FSU Fuse F79, so, I'll have to look again tomorrow. I have the car outside, unlocked, with the trunk open, charging away on the charger - so I hope it doesn't rain tonight.

BTW, how much is your active & quiescent current?
 

Attachments

#11 ·
At battery car on 13.5 it will go up but not much within spec. In sleep I get odd numbers it fluctuates about .75 but it well drop then rise. Obc shows the alternator at 13.7. So good there I haven't ruled out nav or amp. All I do hear is clicking. Like the actuator flap moving. I'm dead currently going to go buy one of those jumper things sick of asking for jump.

Sent from my EVO using Bimmer App
 
#12 · (Edited)
At battery car on 13.5 it will go up but not much within spec. In sleep I get odd numbers it fluctuates about .75 but it well drop then rise. Obc shows the alternator at 13.7. So good there I haven't ruled out nav or amp. All I do hear is clicking. Like the actuator flap moving.
You don't mention the units - but if you used the OBC readout, you must be talking volts.
Volts are fine if you're testing the final state of charge of the battery - but for locating "parasites" causing that battery drain, you need to look at amps (essentially amps are the instantaneous slope telling you direction & magnitude whereas volts are merely the final integration of the area under the curve). Volts are great to tell you that your final state is a dead battery - but - amps are what you need to isolate parasitic leakage at any point in time.

I'm dead currently going to go buy one of those jumper things sick of asking for jump.
I would recommend against buying a portable car jumper until/unless you FIRST buy a good set of jumper cables and a digital multimeter (DMM)!
Then, buy a good battery charger and a good (long & thick, preferably with an LED on the end for night work) extension cord.

After you have those essential items, then (and only then) would I even consider spending any money on a 'jumper thing".
Personally, I think portable car jump starters are problematic for the following reasons:

  • They cost money, consume storage space, and require maintenance - all of which should first go toward the more essential tools I mentioned
  • They have batteries too - so they wear out just like any other battery - so they're more likely to be dead 10 years from now, than alive, when you need them
  • A 6A charger will charge a battery well enough to start in fifteen minutes (or so) anyway
  • There's (almost) always a 12V battery nearby for emergencies anyway, if you don't have time to charge your battery with the charger
Caveat: I'm not against tools (tools are free), so if you 'really' want that portable jump starter, by all means go get it - but - don't even think about it until you already have:

  • Good jumper cables (thick gauge wire, strong jaws, convenient wrapup)
  • Good DMM (Fluke is my preference - but Craftsman works just as well)
  • Good battery charger (my 4A charger works fine but 6A might be nicer)
  • Good extension cord (mine is 100', LED lighted, and heavy gauge wire)
 
#13 ·
Thanks fr the tips. I do have a decent dmm that's really tuned for auto electrics. Bought on Amazon cheap to. Decent cables as well. I haven't gone into through testing yet however. I live in a apartment so its hard to use a battery tender, or something similar. Perhaps I'll buy a charger just makes me nervous in my home and a very curious cat running about. This car had been good to me and this is her first real pain she has given me. I got the car unhooked now battery its near 3 volts. So it well need a jump. Once jumped she charges up. I will see when I get home if its dropped further.

Sent from my EVO using Bimmer App
 
#14 · (Edited)
It looks like pulling F76 did the trick yesterday, as I no longer hear the periodic clicking sounds and this picture sequence below shows the active and quiescent currents at a much more manageable 2 amps and 80 milliamps respectively.
I never just throw parts at a problem, so, I'll let it sit overnight, with the battery connected, and check it in the morning as the first step in confirmation of our hunch.
 

Attachments

#15 ·
I have attempted to follow this thread but honestly, I would rather replace a CCV than troubleshoot an electrical problem on an e39. Your removal of Fuse 76 appears to validate that the drain is occurring in the heater blower circuit (which includes the FSU). Have you pulled and tested your FSU yet? Even though yours was replaced a few years back, the FSU lacks a track record for reliability. Did you originally replace your FSU in 2009 with a dealer sourced part? If yes and the FSU is the cause of the problem, this would suggest that even dealer sourced FSUs have an expiration date. Just one more thing to keep an eye on...
 
#17 ·
PLEASE IMPROVE THE STEPS BELOW SO ALL BENEFIT!
(Advice is always welcome!)

I think I know what to do; so as to add value with every repair, here's my story, as it unfolds.

History
:
a) I had put in a new FSU in, oh, about three years ago (need to check) <=== here's the thread ... 2/2/2009
b) I had put in a new alternator & belt drive system a couple of years ago (need to check) <=== here's the thread 7/26/2010
c) I had put in a new battery just over a year ago (need to check) <=== here's the thread ... 9/19/2011

I think this is the drill:
Step 1: Disconnect & charge the battery
Step 2: Get the battery and alternator checked out at Autozone
Step 3: If it passes step 2, start looking for parasitic drain by pulling the FSU or its 40A fuse F76 (under the glovebox)
Step 4: If it's not the FSU, then start pulling all 88 fuses, one by one, with an ammeter in series with the battery



For your troubleshooting sequence, I would recommend pulling the FSU first rather than pulling fuse 76 for the following reasons:
1. Pulling fuse 76 will only determine if the problem to the heater blower circuit. This is helpful if we have no idea where the problem arises. But this problem (battery drain) is a somewhat common occurance in e39s.
2. The FSU has historical precedence for causing battery drain. By pulling the FSU, you might identify the cause of the problem immediately.
3. The FSU is much easier to access than fuse 76

If your current FSU is the problem and needs to be replaced, this suggests that even newer model FSUs will not last forever. Good to know.
 
#21 · (Edited)
For your troubleshooting sequence, I would recommend pulling the FSU first rather than pulling fuse 76 for the following reasons
I agree with you and will update the procedure so others don't make the same mistake I just did.
In fact, I just pulled the FSU, after decrying that the Germans are still getting back at us for what we did to Dresden in the daylight, way back in 1945, by designing that diabolical God awful FSU harness connector (which broke, again, in my clumsy hands).
You need three (tiny) hands:
1. One hand to hold the flashlight
2. Another to press the clips on the harness connector
3. And a third hand to pull the fsu away from the harness connector

I would still pull your FSU and check it out. It is the only really accesible component on the heater blower circuit that has a history of causing this exact failure.
For others following this, I concur with Fudman that pulling the FSU is a wiser move than pulling the fuse F76 because of the following:
a) Pulling fuse F76 is a general test while pulling the FSU is a specific test
b) Pulling & replacing the FSU is actually slightly EASIER (if you can believe that) than pulling & replacing the yellow 40A fuse F76.
c) If the problem turns out to be the FSU, you have to pull it anyway to replace it.


How many mile do you have?
I have 112K miles on my 2002 which I had bought still under the factory warranty so I'm only the second owner.

In order to isolate the problem, I'm now going to run some amperage tests with the FSU removed and the fuse F76 back in place.
Here is the replacement FSU I just pulled, next to the original FSU I saved all these years (waiting for a round tuit to finally autopsy it).

did you buy your FSU from the dealer?
Unfortunately, I did NOT buy my replacement FSU from the dealer.
This receipt, from late January of 2009, that I posted to the forums shows I bought it from AutoHauzAZ (before I knew about Max).
 

Attachments

#18 ·
With my issue I bought an oe fsu. However I still have a drain. I agree I did the ccv and would rather do that again lol. My problem its say its not the fsu but something else on that circuit. How are we going to do that. Also ota it just me or its there an abnormal amount of battery drain post as of late.

How many mile do you have? I'm just under 79k

Sent from my EVO using Bimmer App
 
#19 ·
With my issue I bought an oe fsu. However I still have a drain. I agree I did the ccv and would rather do that again lol. My problem its say its not the fsu but something else on that circuit. How are we going to do that. Also ota it just me or its there an abnormal amount of battery drain post as of late.

How many mile do you have? I'm just under 79k

Sent from my EVO using Bimmer App
I have about 110K. And while by all rules of logic, your FSU should be fine since you replaced it recently with a new OE FSU. However, we are dealing with an electrical item which means the rules of logic and physics do not always apply. :rofl: I would still pull your FSU and check it out. It is the only really accesible component on the heater blower circuit that has a history of causing this exact failure.
 
#20 ·
I agree logic goes out the widow. Oddly enough the old one seems to be of the newer style too. I never had fan problems. Just those actuators making noise. So basically I'm going to layer up and get outside this weekend to get to the source. I'm really starting to think its something else.

Sent from my EVO using Bimmer App
 
#22 · (Edited)
Check current draw at battery after 16 minutes (don't open or close doors or do anything to re-start sleep mode. By measuring the current drain now use your education to lead you to the problem rather than start at fuse #1 and go down the line. If current drain is 20 amps then it probably is the FSU. If the current drain is say 3 amps then the infamous fuse 56 comes into play. If not the FSU or fuse 56, then you might start going down the line. I think some have reported 150 mil draw when asleep. Evenh that would be "ok"

Also, you can't check the batteries internal impedance-resistance maybe. Don't go and get too fancy with electrical terms out of context! We don't measure battery impedance ever.

Just suggesting we apply a little more deduction based upon what draw is as measured AT THE BATTERY first and then decide which areas of the car are best suspects. Remove negative battery cable and insert ammeter there in series with cable and battery terminal.

PS. Why go to autozone to test your alternator. Just measure battery voltAge running and not. Also, instead of going to autozone just pull the damn FSU and see if your problem goes away. You'll know in under 6 hours in DVM not used or immediately if current drain is being measured. KISS
 
#23 · (Edited)
Check current draw at battery after 16 minutes (don't open or close doors or do anything to re-start sleep mode.
Hi Bill,
Welcome back!
I'm going to add your advice to the original post (so others can follow your advice).
Thanks!

If current drain is 20 amps then it probably is the FSU. If the current drain is say 3 amps then the infamous fuse 56 comes into play.
It makes a lot of sense that the actual nature of the current draw implicates certain circuits, so I'll add your wonderful advice to the first post above (for the benefit of all).

For example:
a. If it's double-digit current draw, then pull the FSU, and check current draw again.
b. For single-digit current draw, pull F56, and check current draw again.

EDIT: I just tested my active & quiescent current with the FSU removed (and with fuse F76 back in place):
Active period: 1.88 amps
Quiescent period: 80 milliamps
 

Attachments

#24 ·
Congrats! You found your issue. 80 mil is in the normal range for your car. If you just want to be sure, you could plug FSU back in and repeat.

When you personally have an issue with your car, I'm always "here" for someone who has given so much for the rest of us. Thanks and glad you have solved your issue. You can drive with the FSU pulled, but you won't have any heat or cool as the fan won't run.
 
#25 · (Edited)
If you just want to be sure, you could plug FSU back in and repeat
That's exactly what I'm going to do because I haven't been able to reproduce the clicking sound and the concurrent jumping to 14 amps as I showed in the videos in prior posts above. In fact, everything seemed "normal" when I re-plugged fuse F76. I even began to doubt what I had seen - but I watched my own videos and there it was. clicking and drawing current every few seconds.

I suspect it's temperature related or sequence related ... so I need to take the bimmer for an errand with the FSU in, and then watch the battery like a hawk when I get back.

BTW, two (minor) problems happened because of all the connections and disconnections.

1. The negative battery cable won't tighten anymore (I may have overtighted it or stripped it or bent it or whatever - but it was night last night when I realized it wouldn't tighten so I'll look today and snap a photo).

2. The FSU harness connector broke (again), so it now has only one tab and no latch. Oh well, it was a diabolically difficult connector to start with - maybe this makes it easier to disconnect. I'll see.

EDIT:
I WISH there were a good electrical test of the FSU itself, with a DMM.
 
#26 ·
I have broken so many plastic tabs on stuff on my 540, that I do not even hesitate to push the connectors or whatever part (headlight lens, whatever) the tab held back together as tight as I can (have even used vice grips to just hold parts together snug) and use a healthy dab of silicon sealer on the split. It allows for a snug hold, yet will come off easily with a finger nail if you have to disconnect again later. Sounds like maybe your FSU was loose in the connector? You can use the dab of silicon sealer and then wrap the connection with electrical tape for a day to allow silicon to dry and do it's job and then tape will come off without pulling silicon off.
 
#27 ·
Lets see if im doing this right.

1. Car goes to sleep, then unhook neg.
2. Hook positive lead from DMM to neg terminal.
3. Hook negative end to battery post (I have no clamps so I use jumper cable to attach neg to post and - lead to the jaw its tight)
4. make sure positive DMM plugged into dc 10a
5. make sure to set DMM to dc10a mode

Active period wait time 16m I got various numbers but nav is on etc. I want to say .627 though I may be wrong. I forgot to note
quiescent period .176 latches for trunk on door button pressed in no lights

So I unplugged fsu same, unplugged various fuses for nav radio phone etc still same
it will bump up to .183 but seems to stay around .176

Is that within spec? Im not sure you seem to get different numbers then I. However you got a nice fluke. Mine is a Equus 3320.

I have not unplugged the whopper 40a behind glove box. Car is unhooked now. Oddly enough after I jumped it I went for a drive about 30 miles in total. I measured from battery and get about 14.0 with car on. Charging system obviously ok. Now after nearly 30 miles I go and test it again 12.2. So reading a bit, that roughly means 50% charged. Whats really odd is that previously I unhooked battery it was at 2.25v before I hooked it back up and jumped it measured in at 6.25 volts or so. I thought that was strange, but I could be wrong it was much colder that day etc.

Tomorrow im going to warranty the battery as I think its bad. As I have said its unhooked right now. I will measure in the morning. Right now its reading around 12.15.

So my theory is the fsu was the culprit, replacing it worked. However the battery is bad from going dead im sure. Even with the new fsu in place it still measured in at .176. I could be wrong by reading your numbers. Please let me know, thanks!:thumbup:
 
#29 · (Edited)
1. Car goes to sleep, then unhook neg
I don't wait for the car to go to sleep because the act of disconnecting and connecting my battery, with the trunk open, makes "my" car wake up. So, the first step I do is set up the ammeter in series with the battery.
Then I give it about 30 seconds to a minute and then I snap a photo of the "awake" current (with all doors closed and I also set the alarm which activates the little yellow light on the shift lever console).
I come back about 16 minutes later, and the first thing I do is check that the little yellow light is out - and then I snap a picture of the current while the car is sleeping.

Active period wait time 16m I got various numbers but nav is on etc. I want to say .627 though I may be wrong.
You don't say your units again, but I'm assuming you're talking amps, so 627 milliamps seems LOW as compared to mine for the period when the computers are still running (mine are in the 2 amp range, but my trunk light is lit). A lot depends on how many lights you have on in your interior. I set the alarm so as to shut them off sooner. The only light I know of burning is the trunk light when I check my "awake" current.

I unplugged fsu same, unplugged various fuses for nav radio phone etc still same it will bump up to .183 but seems to stay around .176
That's double what mine is, and I thought mine was about double or even triple what other people said it should be, but, as Bill said, it's only 200 milliamps which the battery can source overnight without discharging (we'd have to do the math to see how long the battery can source that - but for you - it would be half as long as for me, with half the current draw).

Is that within spec?
That is a good question. I don't have the spec in front of me. I will have to search my Bentleys to see what the spec is. If anyone has a TIS with the spec, it would be nice to look at it to see how we differ.

you seem to get different numbers then I. However you got a nice fluke. Mine is a Equus 3320.
I doubt it's the meter, as current isn't difficult to measure - so I suspect it's either the vehicle differences or the setup differences (for example, I measure with nothing overtly running and the alarm set and only the trunk light lit).

your battery is toast from being deep-cycled too many times.
I'm told the plates buckle from the heat and bits of the lead mixture crumble off and fall to the bottom of the cell, which can short out plates - and insoluble mixtures of lead form which don't go back into solution. So I agree, deep cycling a car battery isn't generally a good thing for the battery.

(I know, why use a simple word like "sleep" when you can use "quiescent"
Point taken. I simply mean there are two periods, the first one is where everything is off and the alarm is set and the only item overtly running is the trunk bulb - and the second period is 16 minutes later when the little yellow light on the shift console goes out.

What I'd like to have (which I don't at the moment) are two specs:
a) The actual spec for the BMW E39 for sleep current (I was originally told it was 30ma, and mine is three times that, although, as you said and I agree, even three times that shouldn't deplete a battery overnight).
b) Some way of testing the FSU in vitro (I can check resistance, but we don't have a resistance spec to check against).

PS: In vitro means "out of the car". :)
 
#28 · (Edited)
From all of what I have seen, read, etc., you are on the upper end of current draw, but should be "ok". I also agree your battery is toast from being deep-cycled too many times. Every time you deep-cycle a conventional battery (even once) , you lose a little bit of reserve that a battery has. This is why I choose to use a red top Optima deep-cycle marine-type battery. I do not even worry about not having a battery gas vent, but that is my personal risk that I believe is within my "balance zone" of risk/reward. I am NOT going to push it or suggest it to anyone. I have also used the big 1000 amp battery that autozone sells-think it was a duralast. I have used a Red top Optima in my M5 as well as my current 540 with no problems thus far. Maybe if I were in a rear corner collision and built-up gases exploded, I would be telling a different story from a wheel chair, but the Optima is a sealed-type battery to begin with and emits very little gas.

I believe that with a .176 amp draw you would not have a problem starting with a good battery, no deep-cycles to "zero", and leaving your car at an airport for a week- it should start right-up. Now, going on a couple weeks or three weeks, it might be a tad soft. It would be interesting to see which fuse would take the sleep (I know, why use a simple word like "sleep" when you can use "quiescent" and send people who don't do crossword puzzles to the dictionary..um, Bee!) draw down near zero. I would only try pulling fuse 56 and repeating just for sake of seeing what the quiescent stuff is all about.

Oh, you had all the test steps correct. Good job and your meter is likely very close. Even cheapo meters are well within +/- 10% which would only be .017 mils one way or the other. You're right on track.

Hope I made sense as I just woke-up from a great night's quiescent period and still gaining mobility of my cells.
 
#30 ·
So lucky me is back at it today. We are talking ma with my readings above. The .627 is in active mode but after some stuff shuts down like the nav which takes a couple minutes. No lights on glove box open, with the switch pushed in so no light. This includes trunk and door button pushed in. I want this most accurate read possible. Just for the hell of it as im waiting on "quiescent" im going to pop on the old fsu and see if it goes nuts.

I really want to say battery looks fine. It measured in at just 12.10, now the battery never got to zero. I know 12.6 is norm, however its not losing charge on its own. It got to around 2-6volts which I disconnected at that point. Does that qualify for a deep cycle. It may just need a long run at highway speed. I am just thinking here though. Always possible to go to AZ and replace it on warranty. They replaced the last one too.

Ill be back with further updates.
 
#31 ·
I'd like to add to this thread to make sure your ground cable is attached securely to the car in the trunk.

I mention it because for whatever reason, mine had become loose and all the batteries I replaced after the original died after ~1 year. I went through 4 batteries in 4 years before discovering the loose ground cable. I tightened it back down (it was very hard to tighten it, too...for whatever reason) and now my current battery is 2 years old and all is well.
 
#32 ·
So while in the process of troubleshooting my car decided she wanted to help me. How sweet of her.

It was my damn MK3! Not really a surprise as it was on the short list. However it acts really strange. I first went down there after active mode and thought I must of hit the key to wake it up. Reason for this as I opened trunk and latch was engaged so I couldn't close it. The damn mk3 was spinning up and then down. The parking indicator light comes on too. Drawing up to 3 and down to 1.9.

It then goes off, it does no eject disks like others have encountered. So it powers on then off. This also cycles the parking indicator, when the mk3 kicks on indicator lights up, when mk3 powers off so does indicator. Car then drops back down to .172 back in sleep mode. I have now pulled the mk3 and left the car connected to battery.

So this things spinning up and down is draining the battery. Why it comes on randomly I cant answer... yet. I really dont think its the gm module. As I would have other symptoms.

I still think its a little high even with mk3 disconnected still draws .172ma. Old fsu in place the same. The only thing I could get to drop draw by about .10ma was shifting gate illumination. It would be nice to get the .172 down a bit more.
 
#33 · (Edited)
I thought "invitro" meant outside the womb...! Whatever. Don't take my jabs as anything but that Bee. Just playing with you and your linguistic ways~ I just think if one has to explain what a word means, pick a more common one :stupid:

Btw, after a drive, my battery will easily read over 13V with car off.
 
#34 ·
The following measurements were made on my original GKR/BMW/Valeo FSR and the replacement acm Germany FSR way back on 2/2/2009:

Here is what I think each pin does:
#1 = ground
#2 = 12V power, 40 amp fused
#3 = input to fsu from heat/ac module
#4 = output power to the blower motor? (speed 1?)
#5 = output power to the blower motor (speed 2?)

And, here is what I measured between each pin and ground (the FSU body):
#1: Old FSU = 600Kohms, new FSU = 11.2 ohms
#2: Old FSU = 3.02Mohms, new FSU = 1.22Mohms
#3: Old FSU = 2.22Mohms, new FSU = 608Kohms
#4: Old FSU = 2.14Mohms, new FSU = 602Kohms
#5: Old FSU = 3.05Mohms, new FSU = 1.28Mohms
Here are the new measurements on the SAME FSRs today:
Note 1: On the GKR FSU, the black lead of the DMM went on the fins.
Note 2: On the acm FSU, the fins were floating so the black lead of the DMM went to pin #1.
#1: Old GKR FSU = 625 Kohms, new acm FSU = OL (0 ohms to terminal 1)
#2: Old GKR FSU = 3.20 Mohms, new acm FSU = OL (1.21 Mohms to terminal 1)
#3: Old GKR FSU = 2.36 Mohms, new acm FSU = OL (605 Kohms to terminal 1)
#4: Old GKR FSU = 2.15 Mohms, new acm FSU = OL (599 Kohms to terminal 1)
#5: Old GKR FSU = 3.15 Mohms, new acm FSU = OL (1.21 Mohms to terminal 1)

That's weird that the aluminum fins on the acm (plastic) FSU were not connected to any of the pins as my prior tests never mentioned that. So I assume that's a before/after diagnostic test of sorts.

Anyway, for consistency, I measured the resistance to pin 1 on the GKR FSU:
Note: The black DMM lead was clipped to pin #1 for this test.
#1: Old GKR FSU = 0 ohms to terminal 1
#2: Old GKR FSU = 3.65 Mohms to terminal 1
#3: Old GKR FSU = 2.98 Mohms to terminal 1
#4: Old GKR FSU = 2.85 Mohms to terminal 1
#5: Old GKR FSU = 3.66 Mohms to terminal 1

It's hard to conclude much, other than there was a total loss of continuity between the aluminum heating fins of the plastic acm FSU and ALL five pins.
 

Attachments

#35 · (Edited)
Ok and great work Bee. Here is the "problem" with doing it the way you did it. Whether the fins are at ground potential or not is irrelavent. The fins are just there for heat dissapation and nothing else. Electrically they serve no relavent purpose.

*If* pin #1 or any pin for that matter is the pin that will be grounded when plugged in to the receiver socket, it needs to be grounded to get any meaningful readings from it. I know you just wanted to have two FSUs in front of you and to look for differences between the two, you need to have at least one pin of the FSUs hooked to ground. As discrete components just sitting on say a table before you, without being hooked to a real ground, the readings don't mean a whole lot. Because you don't want to plug the FSUs in and measure (I agree with your logic) you want to at least ground a pin and then you can hook your meter between that ground and any pin you want. The FSU has the ability to control what...9 speeds? I don't even know how many speeds our fans have, but let's just say nine for the hell of it. That would mean that if the FSU has four or five pins that each speed uses a combination of one FSU pin or more that one FSU pin. lets just say speed one, two, and three on your heat display involve pins 3,4, and 5 on the FSU. Speeds in the car 4,5,and 6 might use pins 3+4, 3+5, and 3+6 in series to get the additional speeds. Likely the other way around as less resistance would mean faster fan speed unless the resistors inside the FSU are put in parallel rather than series which would result in less resistance that either resistor individually. For example, a 10 ohm resistor in series with a 100 ohm resistor would net 110 ohms. A 10 in parallel with a 100 will be less than the lowest value of either or 10+100/10*100 or 110/1000 or .110 ohms. FSU can act in either way. Resistors in parallel offer greater current handling capability than two in series.

So, what do all these mean re: your test? I dunno, I'm too lazy to think about it! Hook the pin on the fsu that you believe is ground (can be determined using resistance scale back-probing socket pins for FSU to ground). Use a jumper cable between this pin and ground and then compare the other pins to the same common ground.

You are a ground-breaker with absolutely boundless energy, inquisitiveness, and desire to furnish reference information that all can use going forward. Not knowing what circuitry that exists inside the FSU, it would not surprise me that the resistance between ground and the resistive pins or the positive and the resistance pins reads nothing. I wonder if when the FSU fails, people notice the fan quits or runs full speed? You can control fan speed by adding resistance between the fan coil and ground or by adding resistance between the fan coil positive and the positive feed. It matters not whether you add resistance on the positive DC leg or the negative DC leg. You just should have one pin of the FSU at a common connection on the car and then measure between there and the other pins. Better yet is doing on the bench with DC applied to the appropriate pins (both pos. & neg.) and then measuring between pos. and the empty pins and then negative to the empty pins. Also check between empty pins to each other and switch lead polarity as well to see if any diode action is going on in that damn thing!

If someone is willing to send me a good fsu and a bad FSU, I can definitively tell you what failed in the one. Can cut open (with permission) and explain the whole damn thing if given the OK. Remember, our FSUs are simply replacing three resistors IIRC. :thumbup:
 
#36 · (Edited)
Remember, our FSUs are simply replacing three resistors IIRC.
UPDATE:
I haven't done anything yet - so my bimmer has been my daily drive sans the final stage resistor - and there have been zero battery problems since I removed that final stage unit (aka FSR/FSU).

But, I HATE replacing things without TESTING them first! It really bugs me big time.

The first step in testing is always UNDERSTANDING how the thing is supposed to work.

Hence my inaction ...

For some reason, I have trouble 'seeing' how the five-pin FSU diagram can be depicted as a three resistor diagram - but if that's the case - then we should be able to build a test jig that tests the FSU. Right?

a. POWER (12volt, 40amp, DC)
b. GROUND
c. Resistor 1 (high current ?)
d. Resistor 2 (medium current ?)
e. Resistor 3 (low current ?)

Moving in that direction, here is my first-pass guess (perhaps wrong) as to what a test jig would look like. Any ideas on how to correct this diagram and how to build that FSU test jig?

UPDATE:
According to "post #148 here" and "post 21 here", I've updated the diagram below.
QUESTION: What do the dotted lines indicate?
And what do the numbers (4.0, 0.35) next to the wiring colors mean?

Double Update:
I opened a test-jig thread today specifically to formulate an FSU testing jig.
> E39 (1997 - 2003) > Do we have a DIY for how to build a test jig testing FSU/FSR operation on the bench?
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top