Another AC Gremlins thread

[RoryK]

Hi All,

I recently bought a 2003 3.0i e53 X5 with only 64k miles on the clock, one elderly gentleman owner and plenty of BMW Sytner history, but there is a few jobs I need to sort on it to get it back to former glory.

The main problem I have at the moment is the AC, I will start from the beginning and go through what I have done so far:

Problem: AC Blowing hot / warm air at all times.

1. I have done the basics of disconnecting the battery, checking the fuses and clearing down the ecu of any errors etc to no avail.
   
2. First point of all was to have the car re-gassed by my local dealer, system check and no leaks and the correct pressure levels applied - No Fix
   
3. Inspection of the Compressor confirmed the clutch was not engaging when turning on the AC, plugged in my INPA diagnostics software and as seen, an error code under AC confirming the coil was faulty.
   
4. Fast forward 2 weeks and a replacement coil arrives from Germany, I whipped the compressor off the car, replaced the coil and the clutch starts to engage and work as expected, Great! Check my diagnostics software, clear the code and it no longer returns, Perfect! so I take it down to the local dealer to get it re-gassed feeling like a job well done, and 1 hour later I get a call 'Your system has been gassed and it has no leaks, but you are not getting any cold air'
   
5. So I bring the car home and then spend the evening troubleshooting and googling my way through various topics to no real drawn conclusion.
   
6. So this is where I start scratching my head a little, the AUX fan, or the pusher fan.. whatever you want to call it doesn't turn on when when you turn on the AC, from what I have read, and through experience with other cars this fan should kick in as soon as I turn on the AC.
   
7. I have tested the connector and the fan is receiving a 12v feed just fine, the small black line I am assuming is some kind of signal wire that sends a pulse from the ecu, as I couldn't trace the line back to a a relay box and I do not have an oscilloscope to hand to check the signal from this wire.
   
8. There are 100's of posts that would lead me to believe the AUX fan has failed, but I found if I unplug the AC pressure switch, the AUX fan suddenly springs to life and spins up to full speed, but I cannot force it to work on any of its 3 stages via my diagnostics software <--- my First curious ????

With the above in mind, this would suggest that there is a fault with the signal going to the fan.. so now I just need to find out where that bad signal is coming from or why? and for this reason I am reluctant to spend the £££ on a new fan, as I am not entirely convinced it is the issue.

What I have done is ordered a new lower pressure switch, in the thinking that this is not sending the correct pressure reading, in turn stopping the ecu from engaging the AC system correctly as a safety precaution.

But whilst I wait for the new pressure sensor to arrive, does anyone else have any ideas or experience that could point me in other directions? or is there anything I have missed? I have checked out the diagrams on realoem.com and the system is pretty simple so it is a process of elimination I guess, working with the cheapest fix first.

Thank you in advance for your time!

Cheers