2002 330i I had my shop fill the R134 (it was a little low) but the compressor will not kick on. He said to look into the ECU that controls the A/C and that there may be a way to reset it so that it will kick on. Anyone have an idea?
A/C stuff is foreign to me, I like to cruise in the summer with the windows down listening to the beautiful VR6 music. Wifey has a much different take on this… LOL.
Thanks!
Chris
does the electric fan work? the fan has to be on for the ac to kick on.
this is actually why i dont have ac in my e46 right now, lol.
Nope, the fans don’t come on either…
Here is a curve ball for you. What was the temp outside? If i recal correctly the lowest the ac would go was 65F. If the outside temp is below 65F the ac wont kick on. There is always a BUT in there. With the windshield defroster on , the AC compressor should kick on. Though im not sure if that was outside temperature deppendent or not. I had a bad outside temp sensor on my E46 and spent all summer without AC, because the outside temp was reading -40 when it was 80F out. couldnt figure out what was wrong with the AC but once I changed the outside temp sensor the AC kicked right on.
FYI: the condenser fans are actually switched on by a pressure switch in the discharge line of your AC. Bottom line…compressor off= no pressure, thus no fans, compressor on= high condenser pressure thus fans on 
Nope, I thought of that too but it reads the correct outside temp on the dash…
So does the electric fan come on at all? Drive it a bit to get it hot and let it idle, the fan should come on. If it doesn’t, you more than likely need a fan, common failure on an E46…
There is always pressure in the lines hence the pressure switch allows control of the compressor clutch. The fans will come on if the a/c is turned on. The compressor should always run with defrost on because it dehumidifies the air in the vehicle to keep the windows from fogging up. A/c also blows anywhere from 32-40 degrees on a properly working system all dependent on the outside temperature. Most Manufacturers say that 20 degrees below ambient is more than acceptable.
Soo we agree then? Yes the AC will always come on when the defroster is on for the exact reason you mentioned.
The Discharge line, or high pressure line has a switch on it that regulates the condenser fan (little radiator thing in front of radiator). Contrary to popular belief those fans do NOT stay on 100% of the time. If you are driving and your AC system is properly charged the air passing through the condenser will cause the discharge pressure to drop and click off the fan.
Now to the AC clutch:
The suction line or low pressure line has a pressure switch on it as well. That switch also causes your AC clutch to turn on and off…see where im going with this?
Bagel, before you go blowing your hard earned cash on a fan see if you can locate the low pressure switch. Ill see if I can dig out the wiring schematics I had for my E46. Im almost positive it was a basic on/off pressure switch and not the transducer type. If its the on and off type then just jump it and the ac clutch should come on(if the switch was the culprit).
Did you check the clutch it’s self yet?
Sorry got antsy with car talk on the car forum!!! LOL
Lmao! Not at all, just stating some basic facts of AC operation and trying to save the guy some cash.
No I haven’t checked other than visually to see that the compressor clutch is not engaging. My A/C guy said it was a lottle low in R134a so he added some but still nothing. But when i hook up my gauge to the port on the rear-most passenger side os the engine compartment it shows it OVERFILLED. FML.
Hmm, honestly I cant remember for the life of me where the low pressure port on the E46 was. But considering how most commercially available consumer gauges will only fit on the low pressure side id say you found it :D, (assuming it just went on with no modifications lol). I do believe a high pressure issue on the low side would cause the compressor to not cycle but I think that the condenser fans would kick on at that point. Could be wrong. If your compressor worked before the fill up and stopped after, i would responsibly remove/reclaim some of the 134 and see if the compressor starts cycling.