'93 Suburban, freaky intermittent electrical short--won't start during short
#1
'93 Suburban, freaky intermittent electrical short--won't start during short
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)?
#4
CF Monarch
#5
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.
#6
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:
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
#7
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.
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.
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#9
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.
Sparks can indicate a poor or intermittent connection though. Clean the terminal with a wire brush and re-tighten the bolt.
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Rednucleus (October 23rd, 2020)
#10
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: