928 at last

Following Wally's troubleshooting guide....
Freeze switch - One side 12.2V, other side .09 - .10V.
Everything else checks out. 12.2V to/through low side pressure switch, clutch engages and will turn compressor (by hand, belt is off).
Turning compressor feels "rough" (something feels like it's grinding).
So, I think the relay in the head unit is OK, and the compressor is screwed.
If anyone has a different opinion, or concurs, please advise.
TIA!

MainePorsche

Your circuitry voltages, along with the resultant clutch engagement (even if by hand) speaks to all is OK from relay to clutch. I agree with your surmise. I grieve for your compressor.
Sorry Rob.

dr bob

The voltage drop at the freeze switch (12 on one side, none on the other) doesn't square up with finding voltage at both sides of the pressure switch and at the clutch. Something isn't right. Can you retest and report the readings?

MainePorsche

doc,
I thought an asymmetry was normal at the freeze switch connections. After diagnosing that mine was expired, my new replacement did have an asymmetry (though not as much as Rob's) and my system works perfectly (other issues addressed as well).

griffiths

What's the history on the compressor?

j.kenzie@sbcglobal.net

Freeze switch: 12V in 0.1 V out, means an open switch. This sounds wrong. Switch should be closed except below temperature set point. If you jumper the freeze switch does clutch engage? The rough feel to the compressor is also a concern, but even a new compressor won't work with an open freeze switch.
Good luck,
Dave

Alan

Redo the tests - the star trek computer would say: "does not compute" - what you have said is impossible to all be true at the same time with the stock set-up.

Rob - if you had a significant difference between each side - as reported here - it would never work either, the switch would be open/off

Alan

WallyP

"Freeze switch - One side 12.2V, other side .09 - .10V."

How - exactly how - are you measuring the voltage?

Example 1 - red wire on terminal a, black wire on body ground; then red wire on terminal b, black wire on body ground.

Example 2 - red wire on terminal a, black wire on body ground, then red wire on terminal b, black wire on terminal a.

Or something else?

928 at last

Compressor came with the car five years ago......only markings on it are "928 Intl" so I know where it came from.....
Had problems with leaks in the system, got those mostly sorted out and after a couple "Rapid Decompression" issues (first time an "O" Ring blew, (on the rear expansion valve, second time the high side R134 adapter blew) it slowly bled down again and when we went to recharge, the system showed roughly 70 lbs both sides, with no love from the compressor. That was late last summer, so I cut the belt and carried on. Now in repair mode again.

928 at last

Sorry, the readings were with the freeze switch out of the circuit. 12.2V on one lead, .08 - .1V on the other with the ground to chassis.

The clutch was working with the freeze switch and low pressure switch bypassed entirely.

928 at last

Another thing I noted, (and I'm hoping it's just an "O" Ring) was that the low pressure switch connector and boot were just soaked in oil.