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1991 V2500 Suburban losing all electrical power, cont.

The ignition switch wires are good, no corrosion, arcing, and they were tight. The switch could be the issue but I don’t think so. The starter has some butt connectors that I can see so I’ll pull it tomorrow and see, on a plus note the wiring on this is stock other than a radio and brake controller. No trailer park electrical engineering on it! I hate wiring, need to get a Model A with a magneto!
 
If you were moving stuff under the dash and the radio came on that's were your open is.
The butt connectors at the starter aren't causing this particular issue.

Key on grab the fat loom near the fuse box, and wiggle it. If things start blinking of and on you have an issue feeding the fuse box.
Or the bulkhead connector. There should be 2 battery hot wire feeds at the ignition switch.
The ignition switch provides power to most of the fuse block.
The dome and head lamps do not go through the ignition switch.
 
I tbought I was good, and I’ve been driving it every day for the last week and some change without issue. Coming into work this morning it shut down on me twice then once again going from building to building. Whatever it is, it stays off for 10-60 seconds then everything pops back on. I have no clue where the bad connection is.
 
Are there any breakers on the ignition side of the fuse box? I don’t see any on the diagrams but this keeps happening and its all at once, then a long pause, then all back on. Like a switch is being flipped. Changing the ignition switch next week.
 
Hmmm, your description Really does sound like one of those aftermarket thermal circuit breakers,your gonna want to look carefully for one of these. Breakers__42870.jpg
 
There is one on the inner fender but its unhooked. The factory wiring diagram doesn’t show any but something may be added in. I’m out of state and when I get back I’ll pull the dash apart again and see what I can see that I didn’t last time.
 
I'll throw these on here if you don't have them already. Really good schematics for that year. Watch out for any of these little pieces of crap that someone may have stuck in place of a fuse.
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Thats the diagram I have been using and its great. It looks like something in circuit #2 is causing the issue.
 
Simple way to load test a power or ground circuit is to build basically a giant test light. Take a high beam or dual beam halogen sealed beam headlight and set it up with a pigtail and a wire to attach to ground and the wire to the high beam filament you attach to your power circuit to be tested. If the headlight lights up the circuit is good. You can switch the wires around if you need to load test a ground circuit. You can hook it up and wiggle stuff while it is on also. This is the only way to find circuit issue. Normal test lights will light up even if a tiny connection is there and a meter puts no load on a circuit. I have fixed many electrical issues this way.
 
I would try to recreate the problem.with engine running, load the system down by turning on everything in the truck. Then or when it fails quickly move in with that test lite and trace backwards from ignition coil to fuse box.
Also note if your headlights stay on or not,if no then carefully check starter wires/connections.
 
The headlights and dome lights stay on so its the ignition side of the fuse block. The #2 circuit, which points me to the ignition switch but I’m checking it all.
 
I remember our old 82 Suburban would drop the headlights for a few seconds and then they'd come back on (sure felt like a long time!). Replacing the floor-mounted dimmer switch would make it work fine for a couple of years. I'm just bringing that up to say that a switch can have an intermittent open. I don't know that I've seen that with these ignition switches, but anything is possible.

Maybe there is some slop in the lock cylinder, rod or switch mounting that doesn't quite have the switch centered in the "run" position. Things do wear over the decades. Anybody ever clean/rebuild one of these ignition switches?
 
As a last resort I might try. The switches aren't made to be serviced.
If pops apart after, it could short out and start a fire. Think 80's and 90's Furds
 
The new switch is in so time will tell if it fixed anything. But while I was under the dash I thought I’d clean up the rear widow wiring. Someone had pulled the rear window switch
and the rear defog switch, and ran two push button switches for the rear window. Once for up and one for down. I pulled that wiring out and found the stock switch, which is good and the plug which is good and figured I'd hook them up but there wasn't any power to the switch. I traced the wires and pulled up the factory wiring diagram and the pink wire coming from the top of the fuse panel is gone, plug and all. I looked for a bit but its getting dark so I'll try again tomorrow. The only thing I can figure is that this thing had an amp and speakers at one point, and they used that rear window power wire for the amp. The window still works with the key so that circuit is good. I hate wiring.

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No its in the dumpster now, but I took it apart and saw normal wear but no evidence of arcing. The grease was old and thick so a spring detent hanging up causing a loose internal contact may have been happening?
 
Crap! That sucks...Your gonna have to be ready with tools and start diagnosing the moment it happens, like immediately test for power at ignition circuit fuse and see where your loosing power.
As long as it keeps acting up you'll eventually find the problem. It's when the problem disappears that i start to worry.
 
Yea it happened 3 times yesterday, once going 65 down the highway for about 10 seconds, the other two in town. It’s happened once in the garage and was out for 2-3 hours then jumped back on while Inwas tracing wires. There is a dead short or a breaker somewhere failing. Going to get some beer and dig into it tonight and keep looking.
 
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