No dash or tail lights, this is WEIRD !!!!!!!!!!!!!!!!!!!!!!!

[mtnmankev]

83 C20
Once upon a time, I would turn the lights on, they worked until I hit a small bump in the road, then the fuse blew.
Replaced fuse, everything worked again until I hit another bump.
Later, I replaced the headlight switch because all the lights started acting up, and the new switch fixed that.
The lights worked fine for about a month, then the fuse blew again.
Also, cig lighter lost power.
Replaced fuse that was blown, all other fuses are good.
Cig lighter never did have power again so I had to find another power source for it, and the dash and tail lights still won't come on.
Have tried six headlight switches, and all I get is headlights.
Bulbs are good, grounds are good, the connector into the back of the instrument cluster is snug and the connections are clean.
I am at my wit's end trying to think where to look next for the problem.
With summer here, I need to be able to use the truck for night driving when it's cooler.

 

[DoubleDingo]

Have you checked the ground up under the dash on the kick panel? I've heard there is one up there and can cause a mess of problems.

 

[crpntr78]

Go to the drivers tail light and remove the whole set up. there is a ground there that screws to the metal surounding the tail light assembly housing. Check to make sure that ground is good. Had the same problem and so ran a new ground wire and no more problem. Weird how it only effected the tail lights.

 

[Bextreme04]

You have something shorting out, thats why you are blowing a fuse. Find the short, it will usually be in an area where your wiring harness is tight up against a corner or near a connector. This is supported by it blowing when hitting a bump.

 

[mtnmankev]

Checked the ground by the taillight, it's good, the ground cluster by the parking brake is good, friend said he saw a flash of light one time about the middle of the dash underneath when the fuse blew the last time.
Checked the wires and stuff there, all seems good.
It's baffling.

 

[Turbo4whl]

Checked the ground by the taillight, it's good, the ground cluster by the parking brake is good, friend said he saw a flash of light one time about the middle of the dash underneath when the fuse blew the last time.
Checked the wires and stuff there, all seems good.
It's baffling.

It will not be a ground problem, unless the tail light power lead is shorting to the ground wire.

If a flash was spotted under the dash, then that is where the short is. New fuse in, turn on the parking lights and wiggle the wires under the dash.

 

[Bextreme04]

Whatever fuse blew, you need to get a multimeter out and set it to continuity check(you will want to set it so it beeps when you have continuity. Pull the blown fuse and place one multimeter lead in the fuse holder(not the side towards the battery). Connect the other lead to ground.

If it starts beeping, the circuit is currently shorted to ground and you can track down the issue by starting at the farthest connection on the circuit and unplug connectors.

If it doesn't start beeping, leave it connected and go under the dash. Start wiggling wires and connectors until you hear it beep. Give a little shake or bump to components like the dimmer switch and headlight switch. When you hear the beep, that is the component or location that is shorting.

 

[Turbo4whl]

I re-read your post. You have no parking lights at all now?

 

[mtnmankev]

I re-read your post. You have no parking lights at all now?

No parking lights and no instrument lights (they are on the same circuit, obviously).
Brake lights and turn signals are okay (different circuit).
Gauges work fine.

 

[Turbo4whl]

Okay. So you need to check now to see if you have power coming to the headlight switch. Check the plug for a damaged contact. If the parking light wire has been shorted to ground enough times it may have even burnt through somewhere. Now that wire is open.

 

[mtnmankev]

Okay. So you need to check now to see if you have power coming to the headlight switch. Check the plug for a damaged contact. If the parking light wire has been shorted to ground enough times it may have even burnt through somewhere. Now that wire is open.

Headlights work fine

 

[mtnmankev]

According to the diagrams I can find online, the instrument lights and parking/tail lights are on different circuits.

 

[Turbo4whl]

According to the diagrams I can find online, the instrument lights and parking/tail lights are on different circuits.

Headlights work fine

Headlights are not fused with a standard push in fuse. Either a circuit breaker or fuse-able link. Should be 2 power leads, hot all the time to the headlight switch. Recheck your diagram.

 

[mtnmankev]

Is it possible the dome light door switch circuits are a cause?
With both doors closed, the dome light glows very dimly (well, it used to before I yanked the bulb) and it only would be bright if I turned the headlight switch all the way to turn on the dome and courtesy lights.

 

[mtnmankev]

And it doesn't help it's 100 friggin degrees outside, scorching sun and no shade to work under.
Ten minutes is the max amount of time at a stretch before I have to head to the house to cool off for at least a half hour.