# Hissing noise from the A/C?



## rs2k (Mar 18, 2003)

Just took delivery of a new 530i three weeks ago and used the A/C for the first time today. Noticed a whistling or a high-pitched hissing sound with the A/C on. Seems to do this at any fan speed. Turn off the A/C and go with vent only - you guessed it - the noise disappears. It surley can't be the vent motor(s) or the noise would always be present, right?

After several searches on this board, all I've found is this post from 'Emission' as of Sept. 2002...

"The hissing in the climate control is probably related to the A/C (see if it does it just on vent mode). The system compresses R-134 to make 'cold' - it also uncompresses it. You can sometimes hear the compression noises (hiss) from some systems. If the noise is new - you could have problems."

Has anyone else had this same experience? I don't know whether to mention it to the dealership or not. There may be nothing they can do and plus I don't want them to feel like I'm being too picky. Let me know what you all think. Thanks.


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## The HACK (Dec 19, 2001)

It's downright impossible to diagnose this sort of problem over the internet. Your best bet is to visit a dealer.

I've had some issues with the AC and climate control making a sort of whistling or hissing noise on both of my cars, and although the "symptoms" are nearly identical the end result was completely different.

On my blue 323Ci, I first started hearing a light, subtle whistle when the climate control (not just the AC) is on. Soon the sound got louder and louder and then my climate control would go completely wacko and be stuck on either full blast or nothing at all. Turns out to be an end stage resistor.

On my wife's red 323Ci, I first started hearing a light, subtle whistle when the AC is on. Soon (after about 2 weeks) we started noticing the AC performance decrease and then after about a month the AC just completely stopped working. It turns out there was a very slow leak from BOTH the feed and return hose and the refrigerant was leaking out and creating that "hissing" sound.

Then again it may be perfectly normal, because when the AC engages when you have the recirc. in auto mode (assuming you have climate control) the motor will close the vent and the sound of air being recirculated is completely different then when you're drawing in fresh outside air...And THAT could be mistaken as a "hiss" as well.

Just some food for thought.


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## stsmytherie (May 8, 2003)

I had the same two problems as Hack. Took six months to diagnose and was a hassle.

Take it to the dealer and get it fixed under warranty. Start the process now.


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## Rich_Jenkins (Jul 12, 2003)

With apologies in advance for topping this thread, but I encountered EXACTLY this symptom last week.

Car is a 2003 E46 with 3 litre M54 engine, owned since from new, currently 47K miles.

The "hiss" noise is only present when the A/C button is switched on; when de-activated, the noise goes away within 10 seconds.

The "hiss" sounds almost like steam escaping. Its not related to engine or road speed. It's not audible outside the car. It's loud enough that Mrs. Wingspan, driving the car yesterday asked, "What's that noise?".

The A/C seems to work well enough for the season, temps here in Orlando have been between 60 and 70ish lately. I have not gone to check whether the drivers or passenger side vents are blowing air with different temps.

Based on some research last night, it sounds like a case of low/no refrigerant, and its possible that I could recharge it at home e.g. with an Autozone Recharge kit.

Some questions:

1) Any thoughts as to other potential causes for this symptom?

2) The Bentley manual advises trained/experienced personnel work on the A/C system only - is a simply re-charge in this category? The don't elaborate much on this symptom or likely causes, nor do they provide much in the way of advice as to where the low-side fill inlet is located, nor procedures for conducting a fill. I've looked for typical DIYs on this but haven't found a whole lot on the 'net. Any thoughts as to how to do this on an E46?

I'm tempted to just make an appointment with the dealer (Fields, Winter Park, Fl) and let them conduct a diagnostics check. The car is out of warranty, but this service department has been pretty good to me and I believe they have the parts and know-how to fix it. I'm not at the point where I've located a good indy shop yet as I'm just transitioning out of the warranty.

Thanks in advance.


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## Rich_Jenkins (Jul 12, 2003)

wingspan said:


> With apologies in advance for topping this thread, but I encountered EXACTLY this symptom last week.
> 
> Car is a 2003 E46 with 3 litre M54 engine, owned since from new, currently 47K miles.
> 
> ...


Well, I've concluded that ignoring this problem in the A/C is not going to help  so I've booked in at the dealer for an appointment in Feb. Will post back with results.


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## Rich_Jenkins (Jul 12, 2003)

Thought I would post the current results of my attempt at DIY today.

I kept researching this and found a fairly simple procedure to recharge the refrigerant.

I went to the local Autozone and bought a recharge kit ($16.99) and a can of R-134A refrigerant.

Following the instructions on the kit, I was able to re-charge my system so things are much much cooler inside, and the 'hiss' sound is completely gone.

Additional information is at this company web site, in particular the video they had here:

http://www.efproducts.com/instructional_videos.html

I also found this thread helpful:

http://forums.bimmerforums.com/forum/showthread.php?t=317015&page=4

I asked Master Wingspan (age 11.) to snap some pictures, they appear below. (bear in mind we are not professionals.)

Some notes:

- The low pressure recharge port is on the firewall, see me pointing to it in picture one. In this picture I've removed the cap from the recharge port.

- After attaching the kit, it read about 20 psi. This was on the low end. I filled until the pressure read about 29 psi. This consumed the one can I had bought. The next picture shows the kit, with the can attached, on the recharge port.

- The last picture shows the can, plus the fittings on the recharge kit. The car end of the kit is a snap-ring fitment. It will only fit on the Low side. One tip - have your right thumb on the top of the attachment fitting as you pull up on the ring with your left hand, you have to overcome the residual pressure on the line, push down, then release the snap ring.

- Wear safety goggles and gloves.

The process is fairly straightforward.

1) turn the gauge handle upwards, lifting the piercing pin all the way up
2) shake can
3) screw the can onto the gauge handle
4) start engine and set to max cool
5) attach the quick disconnect fitting
6) turn the gauge handle clock wise to pierce the can
7) turn the gauge handle counter clockwise until the refrigerant starts to flow.

Trust me, you will hear this. I waited about 5 minutes before I realized that nothing was coming out. Doh. I had not unscrewed the gauge handle enough.

8) while charging, rattle the can and move it between 12 and 6 o clock
9) continue until can is empty (about 15 mins in my case).

You can check the pressure on the low side while doing this process by screwing the gauge handle all the way in.

I used one can and my lp pressure went from 20 to 29 or so. Not too scientific. I think the whole system is 2.2 lbs of refrigerant, but don't quote me on that.

Car info: Car is a 2003 330i bought from new. I now have about 47.7K miles.

Hope this helps. I did not find a lot of recent DIYs on this, so thought I would post the info.

Oh, I'm going to cancel the appointment at the dealer on Monday. 

DISCLAIMER

I am not a professional mechanic, don't do anything stupid on account of what you read on the internet, you proceed at your own risk, look before crossing etc. etc.


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## Rich_Jenkins (Jul 12, 2003)

Just a footnote for the record: I got another can of refrigerant and checked the pressure this weekend in case it was low. At an ambient temperature of 63 deg F, the pressure on the recharge kit gauge read 27.5 psi. This is in the lower side of the "normal" band so I left it for now. It does blow pretty cold, though...


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## Tangent (Jan 18, 2004)

Had the same symptoms in my 330i. Dealership replaced expansion valve under CPO warranty and the sound hasn't returned since.


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## Rich_Jenkins (Jul 12, 2003)

I was at the tool store this morning and saw an R134a refrigerant "gauge".

Interestingly, the gauge indicated that above 45 psi was "high" and above 65 psi "danger".

A reading of 30 psi would be in the middle of "normal".

I say interesting because I had not actually seen anything that related the Low Pressure reading with "normalcy".

When I put my last (and final) can of refrigerant in the other day (2nd so far) the pressure was right about 30 psi at an ambient temp of 84 deg. The A/C blows cold (44 F) so I think I must be full up.

Just making a note for others in case this info is of use.


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## jfl323ci (Jan 25, 2008)

*Awesome!*

Nice write-up and DIY, Wingspan.:thumbup:

This will be useful as I'm planning to recharge mine, and it does have that hissing (motor spinning?) sound when the a/c is on.


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## silverstare46 (Jan 1, 2009)

*Nioise from A/C*



wingspan said:


> I was at the tool store this morning and saw an R134a refrigerant "gauge".
> 
> Interestingly, the gauge indicated that above 45 psi was "high" and above 65 psi "danger".
> 
> ...


Hello, I just replaced the final stage because my a/c was not blowing air but it was fixed. Before replacing the final stage, I heard whistle sound when a/c was on low. And I found your thread and tried as you said. But when I measure the pressure, it was 35 psi which is good. Can you or any one think about any other cause for this noise? I still have cold air . Thanks and Happy Holidays!


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## Tangent (Jan 18, 2004)

Whistling sound at low fan speeds often means the blower itself is wearing out. NOT a fun job replacing it. It's kind of a 10 pound part in a 5 pound space...


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## renatogjr (Apr 29, 2009)

*Good info*



wingspan said:


> Thought I would post the current results of my attempt at DIY today.
> 
> I kept researching this and found a fairly simple procedure to recharge the refrigerant.
> 
> ...


Good info guys! I will get my 325I done today. I had purchased the R134 but was very worried when trying to recharge the system and the gauge went to RED. I got scared and stopped. Thanks all.:thumbup:


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## renatogjr (Apr 29, 2009)

*Good info*



wingspan said:


> Thought I would post the current results of my attempt at DIY today.
> 
> I kept researching this and found a fairly simple procedure to recharge the refrigerant.
> 
> ...


Good info guys! I will get my 325I done today. I had purchased the R134 but was very worried when trying to recharge the system and the gauge went to RED. I got scared and stopped. Thanks all.:thumbup:


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## MalibuMafiaV (Jul 7, 2005)

sigh... these recharge kits are $35s now!


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## imintatters (Jun 27, 2014)

I'm sure the gauge helps but is it necessary? ****s expensive lol. How will I know if its full?

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## Rich_Jenkins (Jul 12, 2003)

^^^ What is the temperature of the A/C outlet when the dial is set to three blue dots with the system set to max cool?


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## imintatters (Jun 27, 2014)

MMME30W said:


> ^^^ What is the temperature of the A/C outlet when the dial is set to three blue dots with the system set to max cool?


I gave in and got the good one they had there

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## imintatters (Jun 27, 2014)

Now my A/C is blowing cold air
Ahhh relaxing and my little girl get cold air in the back

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## paulg (Oct 5, 2003)

llando88 said:


> Thought I would post the current results of my attempt at DIY today.
> 
> I kept researching this and found a fairly simple procedure to recharge the refrigerant.
> 
> ...


In California, if you buy the can of refrigerant and the hose assembly separately, you will also need to buy an R-134-a Recharge Hose Adapter. Cans here have a valve built in to stop half empty cans from ...emptying once removed from the hose assembly. Cans outside of Ca are pierced by the hose assembly.

I did run into a small problem when I removed the hose from the fitting on the car. The valve did not "pop" back into place and was releasing/hissing refrigerant. I pressed the valve (looked vaguely like a Schrader valve) with the tip of a key and after a few tries it popped back into place.

I think it's fixed. :eeps:


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