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'07 Cobalt. A/C clutch fuse was blown. The clutch circuit now reads open to ground, so it seems something catastrophic happened. I am considering what a repair would involve.

The schematic (below) shows two clamp diodes for the clutch coil - one internal to the clutch, the other in the fuse block. Meter-testing the circuit with polarity reversed also reads open, indicating that the diode(s) are non-conducting. So, it/they would need replacement.

The problem is, I find no diode on the fuse block. IDK why there should be two diodes anyway, so I wonder if this might be an error in the schematic - maybe a cut/paste from an older design, where the (single) diode was in the fuse block. In support of this, GM once had a plug-in diode that looks designed to fit fuse block type connectors.

So, my question: is there really supposed to be a diode in the fuse block?

OEM schematic, fr Alldata

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  • Maybe an optional diode in the fuse box allows the use of a compressor that doesn’t have a built in diode.
    – HandyHowie
    Jun 19, 2022 at 22:36
  • When you tested the continuity of the diode, did you have the multimeter set to the diode testing setting?
    – HandyHowie
    Jun 19, 2022 at 22:37
  • Did you test continuity directly across A and B on the compressor clutch?
    – HandyHowie
    Jun 19, 2022 at 22:39
  • @HandyHowie - (a) I could buy the 'optional diode' theory, if I found a place for the diode in the fuse box. But, I don't. (b) yes, diode setting. (c) no; it looks like the fender liner has to come off to get at the connector (or anything else on the compressor). I'm avoiding doing that.
    – George
    Jun 20, 2022 at 2:11
  • Interesting that the 2008 version doesn't have the diode in the clutch ww2-secure.justanswer.com/uploads/BM/bmaxwell8686/…
    – HandyHowie
    Jun 20, 2022 at 8:33

1 Answer 1

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Just to keep this from popping up in the future ...

  • It looks like some GM makes/models/years did have a clamp diode in the fuse block. I'd guess that's why it shows in my schematic.
  • If there was a diode in the fuse block, it appears it would plug in like fuse. There isn't any such in this car, so I don't have one - the only clamp diode is the one (presumably) across the clutch coil.

End of story.

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