'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

  • 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


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.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .