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Discussion Starter #1
Hi, I'm looking for a sanity check here...

I just had my AC hoses rebuilt, and system recharged on my '92 900 vert. I had a couple days of AC, but then nothing. I hear the AC fan, but no loading of the engine, and I don't hear the compressor clutch kick in.

A local shop jumpered the coolant switch, so that's not the problem (unless I really need that re-installed?). I followed some diagnostic instructions I found rooting around, and here's what I found.

Dryer switch OK. Measures closed. Jumping leads turns fans on, but not compressor.
Coolant Temp switch - jumpered as above.
Anti Freeze switch - maybe?

Relay Tests:
Battery at #30
Bridging #30 - #87B Compressor kicks in!
Bridging #30-#87 - already know fan works.
#31 seems adequately grounded.
#86 - No power...
#50 OK
#15 power
#16 - didn't check (protecting ECU...)


From the schematic, with no power on #86, but working AC fans, this only leaves the anti-freeze switch. If this is as bad as the fuel pump relay to get to, I want to be sure...

Thanks
 

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...this only leaves the anti-freeze switch.
Not so. The process of elimination only works if you include everything.
For example, have you checked the timer function of the A/C relay? You have to account for that in testing. WOT function? You checked the expansion valve function? Charge level?
You can't just jump relays, then jump to conclusions.
Does it all work properly with the anti-frost switch jumped?
Take it to the guy who charged it. He's supposed to have a refrigeration license.
 

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Discussion Starter #3
Not jumping to conclusions. based on the schematic, I've got power upstream of of the freeze switch, no power at the relay, and I can engage the compressor clutch with a jumper.
I was only looking to verify that it's worth the time pulling the knee bolster out so I can get to the switch to check it / jumper it. Hate to have to go through that trouble without reason.
 

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Discussion Starter #4
So, it was the anti-freeze (evap thermo switch), or probably more accurately, the connector?
Cleaned things up a bit, now compressor clutch engages, and cold air flows.

Will keep an eye on it, and if it becomes intermittent, I'll look at replacing it, though that looks like a job in itself.
 
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