# F20 Cooling Fan



## tom13 (Jan 13, 2021)

I have a problem with F20 318i 2015 N13 engine radiator cooling fan. Engine running (hot) fan switches on low speed with AC switched on. Start and run engine (hot) fan just doesn't switch onto high speed mode. Engine coolant temperature (reading from instrument cluster through unlock mode) increases to high level fan does not switch on (90 + Deg C). Under bonnet LHS of car (RHD car) fuse #26 (temperature symbol on fuse diagram), remove and reinsert the fan switches on high speed - engine cools down due to increased airflow. Stop engine switch engine back on, fan doesn't switch back on to high speed. Relay replaced (even though it is probably OK) there is voltage on the solenoid side socket pins and fan works high speed mode via jumping relay socket (as in switch across the 2 heavy wires providing power to fan). Relay seems slightly warm even though fan off, could be nothing. If unplug relay and replug back in (engine running) fan switches on high speed mode. Engine off, engine back on - no fan. It seems like coolant temperature sensor is working (gives readout in car, is this same sensor in the circuit which operates the fan?), seems like relay is ok, all 4 x fuses that are associated with fan symbol OK (multimeter checked). Fan seems ok (it works both in low speed mode and high speed mode just not switching on when engine hot). Guessing i'd say there is a problem with the computer logic to the fan or sensor problem (if different sensor - but if temperature is getting to computer and output to instrument cluster surely sensor is OK), the relay has the potential to switch fan on, the fan and fuse ok, temperature sensor ok ? (unless there are seperate sensor for fan logic input). Haven't checked fault codes from the OBD2 yet or replaced temperature sensor in back of engine (seems epic from U-tube videos to change this out), or maybe it is a dodgy wire not giving good signal to fan (like some other posters have problems). Any help of things to try appreciated.


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## mr_bean (Mar 20, 2009)

Stupid question: Does the engine ever overheat (warning on dash)?

Honestly, I would be surprised if the high speed was supposed to kick on ~90C. That should be reserved for higher temps.


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## tom13 (Jan 13, 2021)

update... been up to 111deg c (yikes) as recorded on dash readout . checked signal wire going from fan to engine computer (resistance), wire good, seems like other people have problems here, have not checked signal output to fan with ossciliscope. air conditioning on fan runs slow, air conditioning off fan stops, with engine running - cut and reconnect circuit at fuse ( temp sensor) or relay fan goes high speed. is there any way to find out how engine computer manages fan speed ? eg: cuts in at temperature x.


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## mr_bean (Mar 20, 2009)

So here's what I've dug up. In short, I can't find anything correlating engine temp to fan speed. It's more complicated than that because it also depends on things like A/C load and vehicle speed.
The DME can control fan speed like a dimmer switch, there is no set low speed and set high speed, it's variable. As you mentioned, it might be curious to probe the signal wire to the fan with an o-scope to see the PWM signal and see if it varies with engine temp.
Pulling the temp sensor and/or fan relay is throwing the DME into limp mode which is why the fan goes full speed when you plug them back in.
Your best bet is to get a computer with ISTA installed hooked up to the car so you can manually activate the fan at a desired speed through the DME to make sure it's functioning properly.
And again, if you aren't getting any overheating warnings on the dash, then what is the concern? 120C is considered too hot and will trigger a warning.


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## tom13 (Jan 13, 2021)

I read that the engine operating temperature depends on which driving mode the car is in, eco mode, sport mode = different operating temperatures. Will do experiment to see if the fan comes on in different mode and at what temperature. I just find it odd that if the maximum temperature is say 117 deg c, then why doesn't the fan kick in at 111 deg c, not even on low without A/C going when it goes to low speed mode. OBD 2 scanner coming next week will check for fault codes also.


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## tom13 (Jan 13, 2021)

update: plugged in obd2 reader (AP200M). reader seems to give all the sensor data also in live stream, fault codes, and reset fault codes. * fan signal via OBD2 seems working, when A/C switch on computer signal to fan goes to 20-40% and fan runs slowish like you'd expect. coolant temp sensor seems ok giving what reading you would expect as engine warms up and at ambient before start. all other sensors and readings seem normal. only thing is fan doesn't come on without A/C on and temp keeps getting hotter. next action is to find out exactly what parameter the ECU tells fan to switch on without A/C on....then check all those sensor inputs (I could be missing something). local BMW service centre "fan should definitely come on at about 90 deg c. ... not much help, they can check computer $242, change coolant $$, change thermostat $$, replace water pump for some many $$$. I think all those things are working a-ok and driving down road with some ram air temperature comes back into control ~100 Deg C. going to try email Germany next, there must be a table somewhere in the documentation with these basic engine parameters in it to check against.....all internet people so far is anecdotal stuff like, temperatures are between x and y which is no help because if fan is supposed to be switch on then it seems like it is the computer which is not telling it to (ie a software problem - noting that the computer tells fan to switch on with A/C but not without A/C - up to 111 deg c coolant temperature in any case). changed also to sport+ mode to see if fan cuts in earlier but no it does not.


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## tom13 (Jan 13, 2021)

update: obd2 live data..., fan signal and fan very low speed cutting in at about 110-110 deg c(no A/c) - car not moving, engine rpm increased slightly. driving no fan but normally operating about 105 deg c (35 deg c day uphill). no response yet from bmw factory in germany.


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## XesbyecroF (Apr 8, 2021)

Did you check your oil temps?mine (116! Remaped) eco 111c comfort 110c sport sportplus 108c mever seen over 112c i check my temps from the day i bought it..


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## afy511 (Oct 10, 2019)

tom13 said:


> I have a problem with F20 318i 2015 N13 engine radiator cooling fan. Engine running (hot) fan switches on low speed with AC switched on. Start and run engine (hot) fan just doesn't switch onto high speed mode. Engine coolant temperature (reading from instrument cluster through unlock mode) increases to high level fan does not switch on (90 + Deg C). Under bonnet LHS of car (RHD car) fuse #26 (temperature symbol on fuse diagram), remove and reinsert the fan switches on high speed - engine cools down due to increased airflow. Stop engine switch engine back on, fan doesn't switch back on to high speed. Relay replaced (even though it is probably OK) there is voltage on the solenoid side socket pins and fan works high speed mode via jumping relay socket (as in switch across the 2 heavy wires providing power to fan). Relay seems slightly warm even though fan off, could be nothing. If unplug relay and replug back in (engine running) fan switches on high speed mode. Engine off, engine back on - no fan. It seems like coolant temperature sensor is working (gives readout in car, is this same sensor in the circuit which operates the fan?), seems like relay is ok, all 4 x fuses that are associated with fan symbol OK (multimeter checked). Fan seems ok (it works both in low speed mode and high speed mode just not switching on when engine hot). Guessing i'd say there is a problem with the computer logic to the fan or sensor problem (if different sensor - but if temperature is getting to computer and output to instrument cluster surely sensor is OK), the relay has the potential to switch fan on, the fan and fuse ok, temperature sensor ok ? (unless there are seperate sensor for fan logic input). Haven't checked fault codes from the OBD2 yet or replaced temperature sensor in back of engine (seems epic from U-tube videos to change this out), or maybe it is a dodgy wire not giving good signal to fan (like some other posters have problems). Any help of things to try appreciated.


I have the same issue. When I go beyond 120KM/H the engine warning came up saying engine too hot, drive moderately


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## Alpha W0lf (8 mo ago)

tom13 said:


> update: obd2 live data..., fan signal and fan very low speed cutting in at about 110-110 deg c(no A/c) - car not moving, engine rpm increased slightly. driving no fan but normally operating about 105 deg c (35 deg c day uphill). no response yet from bmw factory in germany.


 Estimated colleague, Did you find out what was the problem? I have exactly the same issue Thank you


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## afy511 (Oct 10, 2019)

My overheating issue got solved. It was the PCV membrane issue. The car overheated only when accelerated beyond normal rpm say like speed above 100 kph and cools down when taken off from accelerator pedal and here is how I fixed it


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