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My AC Compressor clutch doesn't engage unless I directly connect it to the battery. It has plenty of refrigerant and I don't believe it is the low or high pressure cutoff switches. Here is the behavior I am seeing.
  • I see voltage across the control inputs on the A/C enable relay.
  • If I jumper the switched circuit on the A/C enable relay socket while there is a diode in D101, it immediately blows the 10A mini fuse.
  • With a diode in at D101, both sockets of the connector going to the A/C Compressor Clutch show continuity to ground.
  • Without the D101 Diode, only the black wire shows continuity to ground.
Is the ground connection I'm seeing expected behavior for a diode or does this sound like a bad diode? Perhaps maybe a ground short somewhere between the relay and the diode? I must admit I am fuzzy on the expected behavior of the diode in this circuit and as I am typing this I am wondering if I got the connections wrong on the relay when jumpering it. I don't think I did but am not going to do it again until I get some more fuses. When I first started testing this, the 10a mini fuse was fine. I did not blow it till I jumpered the relay.

Any suggestions on how to further debug or fix this issue would be appreciated.

Thanks

View attachment 285433
Have you tested the diode? They allow dc current to flow in one direction only. If current is flowing in both directions, it is bad.
That looks to be one problem, as it doesn't appear that with the diode in place, both sockets of the connector going to the A/C Compressor Clutch should show continuity to ground.
I'm not certain that is what is causing you to have to jump the relay in the first place however. That too, may be bad.
 

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If I'm reading what you are doing right, remember voltage is an expression of the potential difference in electromotive force. This is measured in an open circuit. When you insert the relay, you should have a closed circuit, thus current running through it, negating a voltage at that point. At least so long as your air is turned on. If it's off, you should again have a voltage.
Looking at the schematic you posted, it shows the Low Pressure Switch to be "closed" as well as the High Pressure Switch. If you trace the route of current, the HPS would need to be closed to allow current to travel from Power Distribution Cell 10 in the fuse block, through the HVAC controller, through its self, to the VCM, to the relay, to the under hood fuse, back to the relay power switch, which would allow to go to the clutch, then to ground at Ground Distribution Cell 14
If the LPS is also closed, then if you trace the path, it goes directly to ground from the VCM, to Ground Distribution Cell 14.
Maybe that's what's throwing you off? I'm not entirely sure since it's pretty vague on the path of current through the VCM. The LPS could be the path to ground for current coming from the under hood fuse box, passing through the a/c enable relay.
Verify which is correct.
As far as connectors go, if they're warm they're softer and less likely to break, I've used small screwdrivers to push the lock tabs down and sometimes had to pull with pliers on the connectors, not the wires, and squeeze gently. Extra hands help if you have them.
Also, if you have good sharp probes on your multimeter, you can often insert the probes behind the connector, where the wire goes in at, without pulling them apart. If you test this way, be sure to test both sides of the two connector halves for each wire tested. (I hope that makes sense.)
I don't know if any of the previous 2 suggestions on connectors will help if you are really trying to work on the VCM.
 
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