Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Got a 2004 BMW 325XI in the shop. Customer states the compressor clutch does not engage. After scanning the system I find a code 20 in the IHKA module. Code is useless as there is no info to be found on it anywhere. If cleared it returns right away, so hard failure. I decide to move on with testing and check the obvious. Freon to spec. AC request to the pcm is there. I then notice that this car has a clutch fan and a pusher electric fan in front of the condenser. Well, this is a three wire system which has a power and ground and then a PWM signal to control the speed of the fan. I scope this line and see a pattern, indicating the pcm is attempting to turn it on. I then attempt to turn it on via the bi- directional control of the scan tool. Still nothing. I then get away from the fan as I am quite sure it is faulty at this point. I then command the AC clutch on, which is works and blows ice cold. Pressures are good. So, my question is this. If there is a faulty condenser fan on this model, will it stop the pcm from engaging the AC clutch due to the risk of excessive pressure?
"The man who says it cannot be done should not interrupt the man doing it."
When the AC clutch engages does the condenser fan start running? Or is it dead.
I could possibly see a protection strategy there to prevent over pressure.
I'd verify the fan is faulty and get it swapped out on principle, but inform the folks it may not be the root cause. Gotta fix what's broke first, Right?
I've heard of BMW's using this kind of protection strategy with their AC systems, so I wouldn't be surprised if the fan was the root problem. Not sure about the construction of this fan assembly, but is there a way to substitute a load (like a headlight) for the fan motor? Just to see if it makes everyone happy.
What kind of pulsing did you see on the fan control wire? If the fan really is the problem, then I'm wondering how the failure is getting communicated from the fan module to the IHKA module. One wire would mean a LIN network:
No this fan is dead. I agree with your idea of fixing what is broke, as this will cause a problem if the AC does engage. However, I want to be certain of the root cause first. It seems that no one can confirm if this is a strategy to protect from overpressure of the system or not. I feel it could well be the case...but looking for some sort of confirmation.
"The man who says it cannot be done should not interrupt the man doing it."
Tyler, I would imagine for this to be the cause, the pcm would have to see a lack of airflow from that condenser fan when it is commanded on and then disable the engagement of the clutch. It is terrible that there is no diagnostic chart for this system available anywhere that I can find. The fan is certainly a duty cycle system, as I have repaired them before on BMW vehicles, but the strategy is where I am having second thoughts.
"The man who says it cannot be done should not interrupt the man doing it."
Are you on iATN? I found a couple TechHelp posts that talked about the auxiliary fan interrupting compressor engagement. I can link you if you'd like. I'll bet that fan module is communicating a fan circuit problem as soon as the key goes on. That's why I was curious to see if we could fool the module into thinking everything's A-OK.
I know on the the BMW systems in the MG- Rovers I work with if the fan won't run the AC cuts out after around 1second.
You could try testing if the AC works when switched on above 30mph road speed as the condensor fan is switched off above this speed.
On fully automated climate control models the system can run a self-diagnostic by pressing the AC Auto and Air Distribution Mode while the key is turned from position 0 to postion 2. The test should be done it with bright light shinning on the sunlight sensor.
I haven't a clue about fault code 20 means but
Code 00 is no fault found.
Fault codes 11 to 14 are assorted temperature sensor faulta.
Fault code 21 & 22 are solar sensor faults
Fault code 31 &32 are air mix motor faults
Fault code 33 is distribution motor fault.
" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)
A 3 wire fan control module. The control wire to pcm is pw modulated.
What happens to the fords is that the controll wire corrodes till it breakes. Then the output monitor see no voltage on the wire and the ac clutch will not be commanded on.
If this is not your case, than I don't see how the pcm sees that the fan is not running.
Well, he is supposed to bring the car back to me to run through it some more. I will attempt to drive it over 30mph and see if the AC engages then.
As for the wire corroding, I will say no because there is a signal being produced there from the PCM. So everything is good from the pcm to the fan. Perhaps it sees current draw when the fan is running? The downside of working on EU vehicles is the lack of information....
"The man who says it cannot be done should not interrupt the man doing it."
Truth, I don't know how these things get fixed sometimes.
Did some more research, more confirmations on a fan failure preventing compressor engagement. Just thinking out loud, maybe get a used fan assembly and just plug it in? See if the compressor engages.
Tyler wrote: I've heard of BMW's using this kind of protection strategy with their AC systems, so I wouldn't be surprised if the fan was the root problem. Not sure about the construction of this fan assembly, but is there a way to substitute a load (like a headlight) for the fan motor? Just to see if it makes everyone happy.
What kind of pulsing did you see on the fan control wire? If the fan really is the problem, then I'm wondering how the failure is getting communicated from the fan module to the IHKA module. One wire would mean a LIN network:
Yes, I have recommended that we replace this fan assembly and was told it is too expensive of a repair. So...I guess I will not be able to confirm if this is a fix. I do appreciate the knowledge guys. It would be nice to have some of this information available to us in the field so we do not have to guess at the strategy they are using. The longer I do this, the more questions I seem to have.
"The man who says it cannot be done should not interrupt the man doing it."
It would be nice to have some of this information available to us in the field so we do not have to guess at the strategy they are using. The longer I do this, the more questions I seem to have.
JoesAutoTech wrote: Yes, I have recommended that we replace this fan assembly and was told it is too expensive of a repair. So...I guess I will not be able to confirm if this is a fix. I do appreciate the knowledge guys. It would be nice to have some of this information available to us in the field so we do not have to guess at the strategy they are using. The longer I do this, the more questions I seem to have.
I'm surprised! Customers will drive with ball joints falling out, on three cylinders, overheating, but ALWAYS fix the AC.
No worries on the fix, sir. I definitely learned something from this one. We really do get screwed when it comes to the Euro makes
Topic Author
