Air conditioner, coil, electrical issue

MIGILLICUTY

MEMBER
2000 JEEP GRAND CHEROKEE
4.7L
V8
AWD
AUTOMATIC
173,000 MILES

Hello, My air conditioner compressor coil will not engage. The compressor itself works if I unplug the coil and run jumper wires from it straight to the battery then the coil engages and I get nice cold air. The coil resistance is 4.0 ohms and draws 2.3 amps when jumped to the battery which appears to be in spec from other internet sources. So I believe the compressor and coil are good. Here is where it gets tricky. The wiring harness plug that goes to the coil has 13.4 volts only if its unplugged from the compressor coil plug? Soon as I plug it into the coil the voltage drops to zero? On wiring diagrams it shows the compressor coil is on the ground side of all the electrical components of the entire air conditioner system so I am getting power up to that plug until I plug it in to the compressor. I did a test of running jumper wires from the wiring harness plug over to a Chevrolet Blazer's air conditioner compressor coil (which for sure works) to see if the jeep electrical system will power the coil and the voltage shuts off the same. So something is shutting off the power once it knows it is plugged into the coil I just do not get it? When I have 13.4 volts at the wiring harness side coil plug and unplug either the high or low pressure switch the power shuts off which would suggest both pressure switches work.

6 Replies

WRENCHTECH

MECHANIC
20,758 POSTS

Here is the wire you are following.

https://www.2carpros.com/images/external/81952457.gif

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Friday, August 19th, 2016 AT 5:01 AM

MIGILLICUTY

MEMBER
6 POSTS

Thank you so much for this! I really like how you compare it to a hose with air pressure and a gauge but no air flow that makes sense. It was beating my brains out trying to understand voltage presence without amp flow. Thanks a ton for that diagram too that makes things a lot easier to follow and finally thank you for such a fast response! So am I to prob all the points in the diagram with the test light while the air conditioner clutch is connected even though that is when the voltage shuts off? Is the most likely place to find my "open" circuit in the power distribution side or the junction block side of the diagram?

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Friday, August 19th, 2016 AT 1:35 PM

WRENCHTECH

MECHANIC
20,758 POSTS

Somewhere between fuse #21 in the PDC and the compressor clutch to include the relay.

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Friday, August 19th, 2016 AT 3:07 PM

CARADIODOC

MECHANIC
33,753 POSTS

Sorry that my information got deleted. What I would do is remove the relay, then jump terminals 30 and 87 with a stretched-out paper clip. There's no easier way to turn the circuit on. Now measure the voltage on the paper clip with the compressor plugged in. If you have 12 volts, the cause of the problem is further down the circuit. If you don't have 12 volts, check on both sides of the fuse.

Connector C102 is the next good test point. That's also a good place to find a stretched or corroded terminal. Test on both sides of the connector.

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Friday, August 19th, 2016 AT 8:46 PM

MIGILLICUTY

MEMBER
6 POSTS

PROBLEM FIXED! IT WAS CONNECTOR C102 ! It was not pressed together all the way even though the little snap on lever had cleared the nub, the rubber ribbed seal around the plug was binding on the female connector a little and gave it just enough resistance for the connectors not to touch enough for the A/C clutch! Pressed the two together like the Hulk and wrapped a zip tie around it so it cant vibrate loose! A/C clutch engages just like it should! Good thing I didn't replace the compressor for nothing!