03 e53 aux fan issues
 

As part of my AC trouble shooting I've found what may be a partial cause, the aux fan.
Symptoms:
Will not power on regardless of temp, ac activation or having the temp sensor unplugged at the lower hose.
Does work through INPA.
Was replaced with a used unit 1 year ago when I bought it because it ran continuously if the battery was connected. Not sure when it quit but was discovered investigating AC issues.

I don't see how there can be any issue with the fan if you can actuate it through INPA. It gets voltage, it turns on, it runs, it seems to me the motor is fine.

One question, since I have never used INPA (I only ever used BMW Scanner/PA soft or a Foxwell scan tool), can you run the fan at different speeds through INPA and does it follow the command? I'm just spitballing here; if I remember correctly the fan speed is controlled by PWM output, so I'm just curious if the fan only ran at full speed or nothing, or if it can be operated through its speed range. If the former, it might point to the DME module as being the problem.

yes, you can set the percentage up to 90%. I was able to get responses at different levels.

You would think that if the DME didn't like something about the fan it would set a code as well, but we are clutching at straws here. Very strange that the DME won't work the fan for engine temp either. Something is being missed somewhere and/or there is more to the story.

If it hasn't been done I would really have a look at a wiring diagram and theory of operation/system outline. And would be good if someone with manual A/C could chime in but I don't think it is very common.

Completely agree. But I'm rapidly approaching a threshold of how much I want to chase this. The vehicle has several other smaller things, suspension etc, but I can't have my wife and frequently grandbabies with out so I may have to send it down the road or eave it parked until fall.

Actually I think the manual air might not use the variable displacement compressor so that would rule out the stuck regulator valve. Something to look into.

The compressor only has a single wire, which goes to the clutch. Wouldn't that indicate a fixed displacement?

No, I think the E53s only had the pressure differential operated displacement valve so still just wire to clutch. Later, like E70 (I think) had the electronically controlled variable displacement.

If you don't have a variable displacement compressor that's not compressing then it's likely you have metal bits contaminating the system so there is that.

OK. Thanks. But until I can get the car to turn on the compressor outside of INPA, It's not my biggest priority

Just saying, if you were considering sending it down the road anyway you might take that into consideration.