Driving lights cause weird short in dash

[jonstine]

I have a 1986 M1028 that I bought a few weeks ago. There were some bulbs out in the dash cluster, so I removed everything, changed all of the bulbs, cleaned the plastic/metal circuit board contacts, put dielectric goop in all of the bulb sockets, and put everything back together. I also did the chrome spray paint on the interior of the plastic parts for more light reflection - works well. Anyway, everything seemed to work correctly once I got it all back together, until I drove it at night for the first time. As soon as I pull out the headlight switch to either the parking or driving lights position, the lights on the dash get weird and the fuel gauge takes a nose dive over a couple of minutes. It's not immediate, but it definitely occurs over a 1-5 minute period.

My left blinker indicator stays lit up green the whole time, if I turn on the left blinker it will sloooow blink, but any other time it stays lit while the lights are on. Not the outside turn signal light, just the dash indicator. The highbeam indicators don't work at all, but when I flash the highbeams my left turn indicator will get brighter, and then return to "normal" once I flick off the highbeams. The "Wait" light doesn't work at all now, but it blinks on and off randomly as I'm driving the truck, very much like a short out between contacts. There's gotta be a short somewhere. Indicator operation was fine before I did the cleaning and replacing, so I obviously did something.

Without any real electrical troubleshooting tools (or experience), I am pretty much just shooting in the dark if I take everything back apart. I am hoping that someone here will be able to offer some sage advice. I looked at the wiring diagrams on here, and I see that the headlight and left blinker circuits connect at the opposite ends of the connector on the back of the circuit board (which I also pulled and resetted a couple of times with no change in symptoms).

Anyone ever seen this, or have an idea what the issue could be? I probably need to pull everything back out, but I am not sure where to even focus attention on at this point.

Thanks in advance.

 

[jonstine]

Sorry, I should have added that if I turn the parking/driving lights completely off, everything works fine again. The left blinker will immediately return to normal operation, and the fuel gauge will gradually return to normal/correct operation. I can't test the high beam indicators since the lights are off, but everything seems to work fine until I turn on the lights.

 

[MarcusOReallyus]

Check your grounds. When things get weird, check your grounds. Especially when things get weird if you turn on something that seems to be unrelated, check your grounds.

 

[Barrman]

Check the grounds as mentioned above. Also, reach up there and verify with your fingers that the big electrical plug for the dash is fully seated. There are tabs at the top and bottom. You can feel if they are in all the way.

If everything is checked and you still have the problem. I would suggest pulling the gauge cluster out and looking at the copper contacts for the big plug. They can and do move over next to each other. You might have some sharing electricity when the lights are on.

I think it is a ground issue though.