Compressor Clutch Won't Energise

[white lancer]

BMW X5 3.0i Sport 2004 Auto

My Air Con has never worked since I bought my X5 but due to the recent warm weather I though about getting the system checked out to get it fixed. I was outside in the carpark yesterday and there was one of those mobile air con engineers re-gassing another car so I asked him to take a look at mine when he had finished.

He checked the gas pressure and said it was fine. He did connect the bottle and guages anyway for testing. he said to me the compressor clutch is not energising. he checked the fuses and then put a hotwire on the clutch which energised and the compressor started working pumping ice cold air into the car.

He spent another 20 minutes or so trying to find out what the problem was. he said all of the components seem to be working fine but the compressor clutch wont energise when you press the snowflake button in the car? He said to me that there seems to be an electrical problem? he also said that the condenser fan at the front of the car was supposed to be running but it did not.

The mobile air con engineer then said that he was at the limit of his electrical ability and I needed to take the car to a BMW garage to get it sorted?

Does anyone have any ideas as to where I can look next? I dont have an electrical diagram to check but I was thinking that maybe there was a relay in the curcuit somewhere which i can check?

The heater and blower work fine and I can change the temperature and speed etc

thanks for your help in advance.

[upallnight]

Most likely the aux electrical fan is bad. Do you you have access to a BMW scanner? You can buy a cable and download a copy of BMW Scanner 1.4. Running the diagnostic program will tell you if the Aux fan is bad. If you don't have access to a BMW scanner and don't want to bother with buying a cable you can bring the truck into a BMW specialist who can scan the truck for trouble codes.

[white lancer]

Thanks for the reply.

Does the aux fan need to be running then before the compressor clutch will energise?

[upallnight]

Originally Posted by white lancer

Thanks for the reply.

Does the aux fan need to be running then before the compressor clutch will energise?

The aux fan sends a signal to the DME that it is good. If the DME don't receive a good signal from the fan then it don't operate the compressor.

Here's a post by me on why my ac wasn't working and the FIXED.

http://www.xoutpost.com/bmw-sav-foru...fan-fault.html

[A B Able Truck]

It's alot of reading, but here is some liturature - hope it helps.

Audi A8 project

[white lancer]

that is really useful reading!

I have just run the car and tested the voltage at the aux fan. It read 13.8v on the multi-meter but when I plugged the fan back in it wobbled backwards and forwards a few times before doing nothing.

The clutch on the compressor did engage for 30 seconds or so and there was cold air being blown into the car

I checked the temperatures of the hoses in the engine bay and the high pressure side hose was red hot and the low pressure side hose was cold which suggests that the compressor is working

I guess that because the aux fan was not working the condenser was not working correctly cooling the refrigerant

sounds to me like the condenser fan needs replacing? anyone agree?

[upallnight]

If you have the correct BMW software you can use it to turn on the fan. That will be the only way to tell if the fan is working or not. The fan is pricey (over here on the other side of the pond it could be as high as $500 USD) and it requires 4 - 6 hours of shop time to replace.

[white lancer]

ummmm.... through further research I have found out that the fan has three wires. a positive, negative and a thin wire which provides a square wave pulse from 10hz to 100hz which controls the speed of the fan.

I have tested the positive and negative wires and had a healthy 13.8v there. when I plugged the aux fan back in it juddered fowards and backeards a few times which i guess is something to do with the square wave pulse moving the fan slightly.

now I am not sure if the fan is actually working and it is something wrong with the control side?

I guess a trip to the indy is in order so that they can carry out further diagnostics?

[upallnight]

Your Indy should have the software to command the aux fan to turn on. If they don't have the software or don't know how to do it, find yourself another Indy.