[e90yyc]

I don't mean to be a d*ck, but it will come as a surprise to precisely no one that Firestone's techs don't know what they're doing when it comes to BMW's. An AC recharge should be simple enough, but these cars are so finicky...

I'm curious whether they actually checked pressures or went straight to default based on your complaint it was not blowing cold.

Refrigerant must be filled based on weight, so it's imperative the system be evacuated completely prior to refill. They have the right machine for the job, so if they frigged up it was probably due to human error rather than a lack of proper equipment. This is only a guess, but it's possible the system was overfilled jussssst above the compressor cutoff threshold (system protection). There is both a lower and upper pressure limit. Might be worth asking Firestone how much refrigerant was filled, and then compare this to the sticker under your hood. I can't recall offhand what the correct amount is––best to check.

This is more of an aside, but if you aren't familiar, the compressors in our cars are variable displacement type. They run all the time, but vary the piston stroke depending on cooling requirements.


Okay, so moving onto the other problem: your vent temp isn't what you think it should be... Can you tell us whether the temp issue is a recent thing, or has this problem been there all along? If it's been there all along, it might be nothing more than hot vent ducting that is taking some time to cool down. When I leave my car outside on a hot day, the AC doesn't really feel cold for at least a couple minutes.

Assuming this isn't your issue and something is actually wrong, the best way to diagnose the problem is with software like INPA. You'll be able to read a whole slew of temperatures from various sensors, and see if any are reporting values that are out of acceptable range. I'd be curious what your cabin temp sensor is reading.

Last time I thought my AC wasn't as cold as it should be, I just used an accurate clip-on thermometer attached to center vent. Dealerships use these all the time. It turns out the temp was right where it should be.

Perhaps gbalthrop can offer some more specific advice on what to look for.

Hope some of this helps.