Looking for clarification on A/C clutch, fan, etc.
 

Greetings,
My wife's 03 3.0 X5 recently experienced A/C failure. The A/C clutch won't engage, nor will the auxilliary fan start, either by turning on the A/C button, or by running the car until it reaches operating temp. (OBDII says it is 214 F) The cabin blower works, but of course, it blows ambient air. I had replaced the FSR a few years back for another issue.

I have:

1. checked the two small fuses for the A/C and the 50 amp fuse: all good

2. checked the power at the aux fan plug: 12.5 V dc

3. Until the failure, the A/C was working fine, so I suspect that the freon charge is fine.

I have a couple of questions:

1. Would a fan failure cause the system to not allow the compressor clutch to engage? I.e., is there a fan speed sensor?

2. Is there any way to test the fan itself; I.e. bypassing the system and simply applying 12 V?

3. Any other items to test?

Thanks in advance.

Gary

I'd first unplug the ac compressor activation wire and apply 12v to it. If the compressor kicks on and the AC starts cooling you have a control problem and for some reason the DME is not releasing the compressor. (if it isn't seeing a pressure sensor etc.) If the compressor doesn't kick on with 12v applied the clutch is bad.

Thanks for the reply. I will check it out, as soon as I find out where the compressor activation wire is located. :D

I can't seem to find a wiring diagram (still looking). I see a single wire connected on top of the compressor, but can't seem to find the disconnect.

Any more hints?

Thanks again for your help.

Gary

That is the wire, and the plastic connector where the wire meets the compressor is the th only connector you can get to unfortunately.

Thanks for the reply. I figured that out, and rigged clip from one of my many test leads. When I connect 12V, the clutch engages. When I disconnect, it stops. Doesn't engage when the normal lead is connected and A/C is called for.

When the clutch is engaged manually, the air still doesn't seem cold, though the simple pressure guage I am using shows ~25 psi low side.

***EDIT***

I added some r134 till the pressure was around 30-35 psi, but still not cool air, temp from vent was 85 F.

Any ideas?

I really do appreciate your assistance. :thumbup:

Gary

Just pulled the plug on the aux fan. (At least I assume it was the plug for the aux fan: located just inside the fan shroud inside the engine bay passenger side. ) Three wires, with 13 V applied to the connection. Couldn't get any voltage on the small wire, AC on or not. Signal wire maybe?

Gary

You are correct on the aux fan plug. The two big wires are B+ and ground, the thin wire is from the DME and tells it to come on when it sees it as needed.

And by adding refrigerant you may have overcharged it a bit, the whole system only holds about a pound of R134a (0.98lbs)

If you can find access to a GT1 tester you can read/monitor the pressure sensors, AC request, compressor released, etc. as well as activate the compressor and activate the AUX fan at rates of 30%, 60% and 90%. All through diagnostic requests and component activation in the control module functions.

How long did you leave the AC running when it didn't get cold? Did it produce any condensation drips under the vehicle?

THanks again...one of the plusses of having the inlaws right across the street (aside from the obvious babysitting duties) is that they have an 04 3.0 X5. I simply pulled the two vehicles nose to nose, then spliced via some patch cables my car to his fan. Started it up, set the A/C to max, and Voila! The compressor started right up, then his fan kicked on, and I had cool air. Of course, after a minute or so, the head pressure got too great and the compressor kicked off, but I now know that I have a bad fan.

Now I am off to find a new (or maybe used) fan.

Thanks again for all your time and assistance!

Gary

Just found this thread just to let others know to test the fan you need to pull off the connector to the high pressure sensor of the air con system.

Then if the air con is turned on in the car interior the compressor will not engage but the fan will turn on full blast. Thus proving or disproving the fan at fault. May help some.

I find that hooking up my laptop with BMW Scanner 1.4 and doing a scan can determine if there is a fan fault or not.