The Stupid Electronics Questions Thread

[Jwill945]

Check the tail light circuit boards. Typical GMT400 prob.

Not familiar with these at all. I’m guessing can get a corroded or broken connection. How do I test it?

 

[drifterwanb666]

Not familiar with these at all. I’m guessing can get a corroded or broken connection. How do I test it?

i dont recall ever testing the boards, but check the pigtail from the harness, if you have the voltages at the pigtail then its not wiring, and pretty clear its the board. you can also check the splitter by the spare if you have the 4 prong trailer connector.

 

[someotherguy]

i dont recall ever testing the boards, but check the pigtail from the harness, if you have the voltages at the pigtail then its not wiring, and pretty clear its the board. you can also check the splitter by the spare if you have the 4 prong trailer connector.

There's a disconnect in the harness right near the driver's side end of frame rail. That's also where the "tee-in" style trailer harnesses connect. Best thing when troubleshooting rear lighting issues is to remove any trailer harness from the circuit first.

Then you can check right there at the disconnect - light green is reverse, dark green is right turn signal/brake, yellow is left turn signal/brake, brown is tail lights/park lights/tag lights. Ground test light to the frame or a bed cross support nearby. The ground for the rear lamp harness attaches to that same area.

The taillight circuit boards fail usually from a burnt up socket or sometimes they just get loose and don't grip the bulb well enough anymore. They're a common source of trouble but first step would be to ensure the wiring is good as described above.

Richard

 

[Jwill945]

There's a disconnect in the harness right near the driver's side end of frame rail. That's also where the "tee-in" style trailer harnesses connect. Best thing when troubleshooting rear lighting issues is to remove any trailer harness from the circuit first.

Then you can check right there at the disconnect - light green is reverse, dark green is right turn signal/brake, yellow is left turn signal/brake, brown is tail lights/park lights/tag lights. Ground test light to the frame or a bed cross support nearby. The ground for the rear lamp harness attaches to that same area.

The taillight circuit boards fail usually from a burnt up socket or sometimes they just get loose and don't grip the bulb well enough anymore. They're a common source of trouble but first step would be to ensure the wiring is good as described above.

Richard

Let it ride like it was for about a week until I had to drive across town at night late on a Friday. Pulled the taillight housing off and checked everything. I had a front turn signal that would come on with parking lights but not blink with turn signal and a rear bulb that was good, but wasn’t seated in the housing correctly. Replaced those and we’re good to go!

And for the record, you can test the circuit board at the small exposed spots with a multimeter bit they aren’t easy to see what connects to where, so that info doesn’t do you much good unless you hook it to power and test them that way. I took my impact battery and found the ground terminal and worked around to make sure I had no loss of connection on the board.

 

[CountyLineGarage]

Probably been covered I suppose but fresh opinions never hurt… I’ve got a system I’m wiring up in my toolbox. I’ve run 2 gauge cable to the box from my battery (on my 95 k1500) to a fuse block I’ve built on a sliding tray in the box. From there it will run a 1000w power inverter and a 12v compressor for onboard air.
I have a second battery from my truck that has a lower cca rating than the battery im running now. My question is can I use a smart battery isolator and use this as a sort of auxiliary battery for these accessories to minimize pulling from my main one?
If yes does anyone have any suggestions as to what isolators are any good, and if no are there any issues with running them both (my accessories that is) off of my main battery? I realize alternator probably comes into play as well. I also will have the compressor on a relay/switch so it’s not just constantly running and is also on a separate fuse/circuit than the inverter.
I’m doing this project way overkill so I don’t burn my rig down so any suggestions are welcome.

 

[tinfoil_hat]

Does anyone know what this is and where it connects? I assume it's a ground for something. I discovered it while changing the plug wires. I would guess it's been disconnected for 5-8 years and the truck hasn't burned up yet.

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[Orpedcrow]

Does anyone know what this is and where it connects? I assume it's a ground for something. I discovered it while changing the plug wires. I would guess it's been disconnected for 5-8 years and the truck hasn't burned up yet.

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I think it goes to the back of the head, can you tell where the other end is attached?

 

[tinfoil_hat]

Nah it just comes out of that harness. The connector is large enough to fit over a relatively large bolt. Something on the back of the engine or the dizzy clamp, maybe? I took the lower intake off in maybe 2015 and a mechanic had the intake off plus the dizzy in 2020 I think. I guess I could tie it to just about anything. Pretty sure its a ground and not hot. I guess I should have tested it when I had the air intake off yesterday.

 

[sewlow]

These truck do weird things with poor or incomplete grounds.
Do 'The Big 3'. Your truck will be much happier.

 

[EJ_74]

It goes on the stud behind the head that also retains the wiring harness bracket and ground strap.

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