[Scubudo]

My AC compressor suddenly stopped working about 2 weeks ago. The inside controls function normally, I just can't get any cooling. I was driving at the time it stopped working and up until that time it was cooling great. The cooling stopped working right about the time I came to a stop due to traffic exiting the freeway. I didn't hear or feel anything that would suggest that the compressor imploded.

So far, I have confirmed that the belt is in place and turning, but with a variable compressor there is no cycling of the clutch to indicate if it is getting any signal.
The pressure in the AC is about 152 PSI and doesn't fluctuate at startup (indicating that the compressor is not doing anything).

Fuses all look good.

There are no codes in the ECM.

For reasons I can't fully explain, I am unable to access the cooling module using INPA. Although I am able to control the fan and other control settings with BavTech, but it too doesn’t seem to be able to give me any AC parameters from the sensors.

At this point I gave up and took the vehicle to an indy, who (when I dropped it off with him) said that he had a device he could plug directly into the compressor to control it independently. However, after looking things over (rather than saying the compressor doesn't respond to signal) he instead said that he was "almost positive that the compressor was getting signal". When pressed further he said he was over 99.5% sure" (but didn't explain how he reached that conclusion).
Surprisingly, (rather than giving me an estimate for him to repair it) he instead said that he didn't have the “special tool” to remove and replace the belt. When I told him that I had the tool (rather than accepting my offer for him to use it) he instead suggested that I may wish to replace the compressor myself.
At this point he offered to evacuate the system and said he would reprogram the new compressor after I installed it.
This was the 1st time I have asked anyone to work on this vehicle. I know little about this indy (other than that he seemed polite, respectful, and seemed concerned about how costly repairs on such a vehicle could be. Meanwhile, if he doesn't have the tool to remove/replace the belt (unless the diesels are unique), I assume that he doesn't work on BMW ACs.

At any rate, it seems strange to me that if the AC module were directing the compressor to do its thing, and no pressure was being generated that the ECM would detect a malfunction through the pressure sensors and generate a code. So…before I just start replacing parts, I thought I should find out if anyone here has experienced anything similar.

[328ival]

My A/C stopped working out of nowhere too, sad times wish I could help. Hopefully this comment bring more traction to your post

[e91Owner]

As the e90 gets to be an antique, fewer and fewer people look at the sub-threads. Far more people look at the general forum.

[Scubudo]

IDK why I never got codes, but my problem did turn out to be the compressor.
Per my understanding, there is a part between the compressor and the wheel which is designed to fail in order to prevent a failed compressor from filling the system with metal shavings. I don't know if this part always fails in such events or whether it can fail independently. At any rate, that is what failed.
I was able to replace the compressor myself. The OEM condenser did not have a serviceable drier, so I had to replace that as well. The new condensers have a way to replace the desiccant and came with a desiccant cartridge preinstalled (which I did not realize until the part came in).
Overall, it wasn't a horrible job.
I measured the oil in the old compressor and added back about 1/4 oz extra (split between compressor and condenser). Replaced all of the O-rings.
I had a vacuum pump and was able to pull a vacuum and recharge myself. 2- 12oz cans of R134a which I weighed before and after to discover that I was a few grams over capacity.
I can confirm that had I been trying to recharge by using the pressure, likely would have significantly overcharged my system.
My system now cools just as well as it ever has.
IDK exactly what the computer does to break in a new compressor, but once the new compressor was in, I was able to access the correct module to do the run-in.

150K+ miles on the original compressor seems reasonable to me.

[Tambohamilton]

Nicely done. Yeah, the pulley will shear if the compressor is overloaded for any reason. The pulley runs on its own bearing, so it won't throw the belt etc if that happens...but the compressor won't turn.