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blackbmr325
06-21-2010, 04:13 PM
A buddy just bought a e34 525i, ac doesnt work and the AC button doesnt light up. if the r12 is empty and leaked out, does or should the button light up anyway or is there a electrical issue also?

upallnight
06-21-2010, 07:36 PM
check the easy stuff first, fuse and relay. If the system is very low, the low pressure switch will prevent the compressor clutch from energising. You'll need a set of manifold gauges to properly check out the ac system.

Mark185
06-21-2010, 08:46 PM
Usually, if it is not working, the R12 or R134 has leaked out and the owner drove it for a while in that condition. There are a couple of steps to getting it working again. It is very likely that moisture has gotten into the system and ruined the receiver/dryer. This is easy to replace and costs around $60 IIRC. After replacing the receiver/dryer, someone needs to pull a vacuum on the system to get the moisture out. This step will also determine if there is a bad leak. Slow leaks usually stop after charging the system properly. After pulling a vacuum and verifying no bad leaks, the system needs to be charged with R134. These steps have fixed every old car I have bought with A/C that was not working. I have paid shops $150-170 for this service after replacing the receiver/dryer myself. The last time, I bought a cheap vacuum pump from Harbor Freight and charged it with a couple of cans of R134 purchased at an auto parts store. It worked like a champ.

There can be an electrical issue but that is rare on the E34. The compressor can be bad but that is also rare. These are pretty good systems and easy to repair. A manifold gauge set makes servicing easier but I have gotten good results with the cheap R134 kits that include a gauge.