AC compressor circuit - BMW Forum

av8 · 04-16-2004, 08:22 AM

The AC compressor clutch in my 1984 318i does not engage when the AC is turned on. All other related circuits (idle up, blower) operate correctly. Neither my owners manual or the Haynes manual identify any circuit protection other than a fuse in the panel, which is okay.

Is there an in-line fuse to the AC clutch or is it protected by a relay, and if so, which relay is it? (The relays are not identified by circuit in either the OM or Haynes.

TIA for any and all help.

Mike Bishop
Santa Rosa, California

KC Ron Carter · 04-17-2004, 04:35 PM

There are switches in the two bottom vent selectors. One must be open or the A/C compressor will not get voltage.

On the dryer there is a low pressure and a high pressure switch to prevent system damage if service is off.

Those are the hidden issues used to control the A/C besides the snow flake switch.

On some compressors there is a thermal overload switch but I have never seen one bad.

Later,