Official A/C Thread???

[Dominick]

How about it?
-Like models for compressors and which can be switched in what years and cars.

-A rundown on all the parts and how they work to help ppl troubleshoot.

-Capacities of freon, oils, etc. for different years and cars.

-Weight savings of deleting a/c

-And anything anyone else can think of.

If everyone puts in info they know is right, ill put it all together in an article type deal.

and i have a question, i have an 85 318i and i want to know if i can put any compressor in?

[AdamF 88iS]

The compressors are mostly all interchangeable on cars with old style belts, like E30s.

There are a couple of typcial problems on E30 AC systems. Electronic problems preventing the compressor engaging are usually due to the sliding swtiches for the vents in the dash going out. These cut the AC off if you have the vents closed. The easeist way to fix this is to bypass the swtich by cutting the end of the connector off and splicing the ends together. This fix is BMW approved and was offered as a SI Bulletin back in the days. Other electronics in the system include a freeze sensor in the evaporater (in the dash) that will cut it off if it gets too cold, and another pressure/temp swtich on the drier bottle under the hood that can also cut it off if pressures are too high. But typically these don't have problems.

Problems within the system itself are usually caused by clogging at 2 different points. Number one is the small screen inside the hose fitting for the compressor intake. Its like a mini filter and it will get plugged up easily. It can be cleaned. The other is the expansion valve. You can't clean these, you'll need a new one. If you have a full charge and you're sure the compressor is running, but still can't get cold, this is probably your situation.

Leaks usually occour from the old style evaporater cores. The originals on these cars have copper pipes that are soldered to the aluminum core. Over time these solder joints come loose and blow your charge all over your passenger's feet. A brand new core is all aluminum and will never have this problem.

Capacity of oil: Not very much. Do it by eye when you have the compressor out. It only takes a couple ounces.
Capacity of Freon: The sticker says 2.5 pounds of R12. You can use about 2 lbs even of R134a and get great cooling.

The whole system weighs a little under 50lbs.

[Dominick]

Adam you are my hero!

Lets keep this going, if anyone has any questions post here and i can put it into a FAQ format later on.

[Dominick]

i know where the pressure switch is but how do i jump it?

[jht3]

on m3's and maybe other, there are a few switches that all need to close in order to engage the clutch. they are:

slider on dash
a/c button on dash
low pressure on drier
high pressure on drier
coolant overtemp on thermostat


i had a failed coolant overtemp sensor on the back of my thermostat; it was stuck open. i put a jumper wire in as a temp fix.

it's a good idea to replace the drier if the system has been exposed to air. i understand there's a new style drier that doesn't use two pressure switches. i haven't gotten enough credible info on this though.