Strange AC Behavior
 

Hello, having some weird AC issues in this Texas heat. When the car is engine is cold, the AC works as expected. Blows cold air. However, if the car is parked in the heat, or the engine is hot, the AC stops blowing the cold air and blows warmer and/or room temperature air. Not sure what is causing this. Your expertise is appreciated.

Check the charge, may be low and when there is a load, not enough capacity do to short charge.

Recharged a few weeks ago. Took in for a recheck and it was blowing cold air. Mechanic declared that everything is normal. However, it is an intermittant issue. It only seems to be happening when the car is hot.

The IHKA module will produce BMW specific error codes for the hvac system. Either purchase a BMW compatable OBD code reader or software for a laptop for one of the BMW diagnostic packages. Or visit a Indy to have the codes read. Your typical code reader from AutoZone, Pepboys, etc won't do the job.

Mine does this as well. Usually on days where the inside temperature is extreme. It eventually starts working again so I just leave it be. I was told it may be a lazy shuttle valve in the compressor. E60 uses a variable displacement compressor with no clutch - always on - output depends on shuttle valve position.

It sure got worse today. Initially it was fine, but when turned the engine off to go to a store, it started to act up. Temperature was 95F when it happened. It never got to normal again. Was only blowing warm and hot air with short episodes of slightly cooler air, but not cold as it was initially.

I'll take it to my Indy tomorrow, as he recharged end of April.

UPDATE: went to my Indy mechanic today. Had to leave the car in the sun of about 98F today in Dallas and leave running. Everything was working okay. I had to turn off the AC and shut off the engine for a few minutes for the AC to recreate the symptom. So, if I had not turned off the AC and/or shut off the engine, the AC would be performing as expected blowing cold air!

Mechanic checked the charge, which was fine. Then checked the AC system physically; checking the compressor, fan etcetera, and all were working fine. Then hooked up his computer to check for any error codes. No error codes either. He thinks it is the compressor, but he said that he rarely saw these compressors go bad; especially at 103K miles, which my car has now.

One key thing he mentioned is that the low pressure shows higher than normal, which indicates a bad compressor(??)

Have any of you had to change your compressor?

I had to replace compressor at 70K miles. It started with AC working intermittently and after few months it was totally dead. I replaced the control valve on the old unit first. That didn't help. Installed new compressor. AC was back to normal. I also replaced expansion valve and dryer filter since system was already open and it was inexpensive and easy to do.

Thanks for the info to replace the Expansion Valve and Dryer Filter at the same time. Mine works intermittently as well; working perfectly when the car is cold. With this Texas heat, however, I will die before I let it totally die!

FWIW, mine's been doing it since 2012 and hasn't changed its behaviour. If it gets worse, I'll worry about mine then.