Annoyed by AC Compressor

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JB_JEEP_KJ

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Jul 13, 2020
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Hi,
I am trying understand why my AC Compressor clutch doesn't engage sometimes. The most reproducible behavior is as follows

Start the Jeep from cold, turn on AC - it works, compressor engages
Let Jeep idle for a long time, AC continues to work - Jeep at operating temperature for 10 mins or more.
Turn jeep off and start it up again
Compressor will NOT engage.

I put manifold gauge on, the pressure in the AC at cold start is essentially the same as when I restart. I have to wait a minute for the static pressure to return to balanced state after running the engine (occasionally it take a very long time, maybe it depends on where the compressor comes to rest?)

When I rev the engine and the high pressure side gets to 292 PSI, the electric fan comes on just like it should so pressure transducer seems to be working properly. The fan also goes back off at 227 PSI, again exactly like it should.

The low pressure switch must be working since the AC comes on initially. I monitor the low side pressure and it never drops below the point where the low pressure switch should activate. I wiggled the connector and wire harness just to be sure there wasn't a problem there, the clutch stays engaged.

There really isn't anything in the wiring diagram that could explain this. There are some more global power down things, but they would cause other symptoms.

Does anyone know if there is a thermal cutout switch as part of the compressor itself? I can't see one, but have limited view of the compressor. I am thinking this would explain the behavior, and it wouldn't be shown on the vehicle wiring diagram since part of the compressor.

JB
 

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