Electrical gremlins

[Grumpus Monkus]

So just over 2 years later the ol' girl is up and running as of today. She seems to run and drive fine, but we noticed a few issues:

Tail / brake lights don't work, fuses appear to be good.

Electric windows won't go down, again, fuse appear to be good.

Floor switch for high beams, we get all 4 headlights, and when we press on the floor switch to turn the hi beams off we get no lights at all.

No turn signals

And the windshield wipers like to come on randomly even thought he switch shows them to be off, a new switch was put in when we bought the truck a few years ago because the PO said the wipers don't work. They did after the switch was replaced, but again, now they come on randomly.

Any thoughts?
TIA

[gmachinz]

Floor dimmer contacts get corroded typically-and the high beam circuit runs through it from switch to headlights. As for the power windows, first thing to check is for binding, dried out scissor assembly components-all Windows whether manual or power require at least periodic greasing/inspection. Bad weatherstripping binds the glass travel too. Then there's highly resistive wiring present in the GM design from the start and only gets worse with age. Strands break apart @ the switch connectors, the acrylic jacketing gets brittle and breaks-causing the wiring within to flex and break in areas of movement such as the door-cab boots. Those are the first things I'd check out.

[ripdog28]

Proper grounds make a huge difference. Check all grounds. Body to frame, frame to engine, battery to engine. Lots of info on here.
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[gmachinz]

That year has only one ground for the window circuit and its on the common ground juntion buss behind the lower LH vent and is bolted to the cab....you'll probably see several grounds there for other circuits too.

[Grumpus Monkus]

Thanks for the replies. My next day off is Monday so I'll see what I can track down and figure out.

All the best.

[franken]

A DVM is going to be a friend. Electricity is pretty simple--it needs a path to and from the thing powered. All the electrons flow from the battery/alt to the load and back. When things don't work, the electrons aren't flowing.

[ck5566]

Originally Posted by ripdog28

Proper grounds make a huge difference. Check all grounds. Body to frame, frame to engine, battery to engine. Lots of info on here.
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100X what he said. Grounds are the starting point.

[demian5]

Check for bad grounds or an overcharge condition.

We bought a 50k mile 86 c20 that was really clean, but the low beams and rear lights were blown out. Also, the gauges were not working right (blown resistors on all of them).

Never figured out what caused it, but cleaning grounds and connector terminals seemed to stop it from happening again.

And this was in a So Cal bought, So Cal stored truck.

[bd94s10]

I'm not an expert at wiring but I've rewired a few of my builds. One tool I'd suggest you picking up is a Power Probe. I've been using mine the past week or 2 on my 79 dually trying to figure something out. It comes in super handy especially when testing power window motors etc. It will quickly tell you if you have a good ground or are getting power. This is the one I have from Amazon.

Power Probe PP3LS01 Power Probe III Circuit Tester with PPLS01 Lead Set Kit

I'm with others on this. Sounds like a bad ground.