Update on '88 E28 M5 AC cuts out at high speed

["Foster, Lawrence" <Lawrence.Foster@xxxxxxxxxxxx>]

I spent some more time poking around with my wife's AC problem.  It
turns out that the problem isn't directly related to high engine speed,
but rather a dodgy temperature switch on the compressor.  At a constant
1,800 rpm the resistance across the switch floats between 0 to 2 ohms,
apparently enough to drop the clutch out.  I didn't have a gauge set to
watch pressures, but when I had the system recharged earlier that day
the high side was around 225 psig which isn't too bad if I recall
correctly.

Right now I've by-passed the switch until I can learn a bit more about
how it's supposed to work. My thinking is that the switch is bad as the
readings should be either 0 ohm or open circuit and not some value in
between.  I'm not in a big hurry to replace it as the system needs to be
discharged in order to get to it.  And living in Phoenix I'm not too
interested in running without it either.

Larry Foster

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