A/C Blowing Hot Air
 

The A/C in my wife’s ‘03 X5 3.0i (123K mi) is blowing hot air at highway speeds and at idle. Had the FSR replaced about 3 years ago but the system has never been recharged. I figured the culprit was low refrigerant so I picked up an Interdynamics R-134a recharge kit with built-in gauge. When I got home I went for a test drive and confirmed the wife’s observations.
I did a visual when I got back and noted the compressor clutch was engaging with the a/c on max. Also, the aux fan was coming on about every 30 seconds for 10-20 seconds.
With the engine at normal operating temperature and a/c on MAX setting, I connected the recharge kit to the low side. I expected the gauge to be in the green but was surprised to see it in the red. About 115psi if the gauge can be trusted. I don’t have a manifold gauge set to measure the high side. Outside temp was 87.
I’m stumped. Searched the E53 forum posts and didn’t find anything similar. Any explanations why such a high pressure reading on the low side and suggestions for repairing?
Thanks!

Unfortunately there are many components that make up a
BMW climate control system. It's not so simple to diagnosis
current systems without knowing all the other factors that
contribute to airflow.

Even my 1987 7 series had more components than the law allows
and when it's climate control went on the spritz it was very interesting
seeing all the components it was made of.

Might be good to let someone who has a professional manual
go thru it and see what's up.

Thanks for the reply, QS.

Re-reading my post , the “blowing hot air” is a bit misleading. I probably should have said it’s not blowing cold air. The air coming out is the same as the ambient air temp (and it was hot yesterday). The air isn’t heated, so perhaps airflow isn't a consideration. Apologies for the confusing description.

I’m more curious about the cause of the high pressure reading on the low side. I agree there are more parts involved than one can shake a stick at, but getting your hands dirty (and making a few mistakes) is all part of the learning process.

I’ll hold out a bit longer before taking the professional with a manual approach. The posts in the forum have helped me do brake, CV boot and alternator replacements in the past. I’m hopeful there are some additional troubleshooting steps out there that would help narrow the problem scope down to a faulty component. Whether or not I have the tools, skill or patience to replace it myself is another matter. :P

Wish you the best.......
Keep us informed.

I'll ask the dumb question first - the dial on the dash is set to the cold function correct? (three blue dots showing)?

I just took mine in for a similar issue and the dealer diagnosed a slow freon/whatever the coolant is they use now leak. He evacuated the system and refilled and everything works fine.

I work at breaking software all day. Believe me, there's no such thing as a dumb question (except the one not asked).

Yes. The dial on the dash between the center vents was set to max cool (three blue dots).

Thanks N S.

i am betting on the Thermostat housing...happened in my e60

can you elaborate more on what the thermostat housing consists of?

Hi. How long did you wait after taking the test drive to measure the pressure with the gauge? Maybe the engine was still hot enough to affect the coolant pressure? I bought the Quest R-134a QuickCheck A/C Gauge which had this chart for ambient temp (F) vs optimal (filled) Low Side Gauge readings:

65F 25-35 psi
70F 35-40 psi
75F 35-45 psi
80F 40-50 psi
85F 45-55 psi
90F 45-55 psi
95F 50-55 psi
100F 50-55 psi
105F 50-55 psi
110F 50-55 psi

I hope this helps!

Does it get cold if you drive on the highway? If so then your AUX fan is bad.