From digest.v5.n164 Thu Aug 29 14:40:00 1996
From: Anthony Le <anthony.le_at_wcom.com>
Date: Thu, 29 Aug 1996 14:09:50 -0500
Subject: Re:Air Conditioning (Compressor Clutch)

>>>>>
From: "Matt R. Brumwell" <mbrumwell_at_icx.net> Date: Thu, 29 Aug 1996 00:24:50 -0500
Subject: <E30 M3> Air Conditioning (Compressor Clutch)

The clutch is not engaging on the AC compressor on my '88 M3. The light comes on in thedash and the blower works. The fuse (20?) is OK. I do not get 12 volts on the wirethat runs down to the compressor right by the wiper fluid reservoir. Is the pressuresensor bad? Is this the two prong connector with the white block type pig tail by theview glass, or is it the one with the rubber boot that connects right where the view
glass is.
matt brumwell
>>>>>

They're both pressure sensor. One is high, the other is low. I don't know which is which. High sensor, low sensor, and ice sensor can shut down your AC.

High pressure stops compressor when pressure reaches 363 to 252 psi, and starts again when pressure drops to 320 to 284 psi.

Low pressure stops compressor when pressure drops to 32 to 24 psi, and starts again when pressure reaches 28 to 34 psi.

Freeze protection switch is next to heater water valve in the HVAC unit. Hope this helps.