OldSilverado

Ground lug: tan w/white strip and black w/white stripe. Bolts to back of A/C compressor

This thing sparks when the engine is warm, indicating a short. The engine will not start at that time. When this thing isn't shorting out, the engine starts fine. Engine starts fine with this disconnected. Any thoughts (I don't have a wiring schematic)?

Rednucleus

Where is it's home when connected??

OldSilverado

The ground lug at the rear of the A/C compressor (that's a closeup of that lug in the photo).

kevinkpk

Put a real terminal on it.

Sabino56

seems like something upstream is dumping 12v to that ground. A schematic would help (I've seen them posted for this car somewhere but can't remember) but probably you need to trace the wires back looking for damaged wires. I would think some component failing/shorting out would blow a fuse. Guessing this is a power and ground wire making contact somewhere due to cut/damage/wear. A schematic won't help find that.

OldSilverado

Savbino56, you're thinking along the same lines that I am. Anyhow, I ordered the factory wiring schematic book, just to understand the circuits involved.

So, one more time, here's what happens:

• turn key to start and sparks come to that terminal, indicating short
• disconnect the terminal from ground and the engine cranks right up when you turn the key to start
• intermittent problem, so the two wires rubbing together theory could be correct

Sabino56

btw - I remembered where the schematics were - https://www.gmt400.com/threads/88-95...manuals.43575/

page 160 shows circuit for AC clutch, high pressure switch and assuming ground is for that as ground is to AC - shows that it goes to a fuseable link which may explain why it's not blowing a fuse. There is also a diode across power/grnd on clutch coil - but I thought those things died and were dead, not intermittent. But I'm not an electrical guy so don't know for sure.

OldSilverado

Thanks. Valuable info and link!

I'll take a look as well.

mountainmanjoe

sparks do not always indicate a short. That is a ground wire, and should be connected to chassis ground.

Sparks can indicate a poor or intermittent connection though. Clean the terminal with a wire brush and re-tighten the bolt.

OldSilverado

Thanks MMJ, however, that doesn't seem square with the way the starter won't crank when the ground lug is connected (instead a spark occurs), but if I unhook the wire from that ground the starter cranks right up. It seems more to match this from the wiring manual: