No dash lights!!

[justinbrugg]

1978 Chevy c10 tail lamp and curtesy light fuse blows every time dash lights are turned on. I think it’s grounding out somewhere. Pulled the rear lights (blinker break, rev. Etc) but the fuse still blew. Looking for ideas on where it could be grounding out. All of the gauge lights have been swapped out with led bulbs so it’s not because the bulbs are bad. My running lights don’t work either and I think they are connected in some way with the interior lights. Im out of ideas on where to look so any half ass ideas would help. Thank you!!

 

[PrairieDrifter]

You have to inspect the entire tail light and marker light harness. Inch by inch. Shorts don't just happen.

 

[WP29P4A]

Has any work been done recently to the truck? Any issues leading up to the short? The wiring for the light in the stereo, if shorted or tied to another wire can do what your describing. Even non-electrical parts can cause a short if a wire gets pinched when installing the new part.
Like PD said "Shorts don't just happen". Most likely something changed to cause the short. I've seen stereo installs where they were screwing the amp to the floor and hit a wiring loom and also a fuel line, also seen wires melted from exhaust welding. Also could be something that was done months ago and just now finally rubbed through the jacket on the wire, causing a short.
Another likely culprit is trailer wiring or plug, high percentage of hack installs eventually leading to shorts and poor connections make this a good place to check off the list of possibilities. Also putting single filament bulbs in a dual filament socket can create a short or link between circuits.

 

[justinbrugg]

Has any work been done recently to the truck? Any issues leading up to the short? The wiring for the light in the stereo, if shorted or tied to another wire can do what your describing. Even non-electrical parts can cause a short if a wire gets pinched when installing the new part.
Like PD said "Shorts don't just happen". Most likely something changed to cause the short. I've seen stereo installs where they were screwing the amp to the floor and hit a wiring loom and also a fuel line, also seen wires melted from exhaust welding. Also could be something that was done months ago and just now finally rubbed through the jacket on the wire, causing a short.
Another likely culprit is trailer wiring or plug, high percentage of hack installs eventually leading to shorts and poor connections make this a good place to check off the list of possibilities. Also putting single filament bulbs in a dual filament socket can create a short or link between circuits.

LED lights were installed so shouldn’t be the bulb itself. I think the owner before me had done work to the car. Dash lights didn’t work when I first got the car. Do t know if the running lights worked either. The whole wiring harness had been re plugged by me and the engine bay wiring had been fully re done. Everything works: tach, fuel, temp, Speedo, blinkers, brake lights headlight high/lo, rev lights, front blinkers, and others I may missed. Things that don’t work: rear side signal lights, front running lights, dash lights, courtesy light. There all connected to that switch on the dash. We had unplugged the rear lights at the plug in the back and the fuse blew so the rear lights wouldn’t be the problem. Pulled the plug on the fire wall for the front lights and the fuse didn’t blow. I haven’t done anything with the wiring to the front lights other than re pinning which was don’t correctly. The main plug for the motor alt, and starter I had messed with fully but I’m fairly certain it’s the plug for front lights. Sorry for the long response

 

[justinbrugg]

You have to inspect the entire tail light and marker light harness. Inch by inch. Shorts don't just happen.

The rear lights were unplugged when I was trying to diagnose the issue and the fuse still broke even with them unplugged. So I’m fairly certain it’s not because of them

 

[DoubleDingo]

Out

 

[PrairieDrifter]

The rear lights were unplugged when I was trying to diagnose the issue and the fuse still broke even with them unplugged. So I’m fairly certain it’s not because of them

What is unplugged? Wires still have power without bulbs connected.

 

[justinbrugg]

What is unplugged? Wires still have power without bulbs connected.

I unplugged the plug that connects the rear lights. Fuse still blew which means it’s not causing the problem. Pulled the plug on the firewall that is responsible for headlights, front markers running lights etc and fuse didn’t blow. I’ve not touched the front light wiring on the truck so my guess is it’s either the front lights or something under the dash.

 

[Jgonick]

Pulled the plug on the fire wall for the front lights and the fuse didn’t blow

Sounds like the place to start. BRN-9 wire runs to side markers & front Park/Dir sig lights. Check those lights first to make sure the the bulbs and sockets are good (not shorted out). Inspect the BRN wire ,starting at those lights, making sure it is not grounding out somewhere.

 

[WP29P4A]

Don't assume that the LED lights are NOT the issue. If you have a defective cheap Chinese LED bulb, it could be the source of your issue. I have read several posts here that say you can not use LED bulbs in the front side marker lights because of the way the circuit works. To trouble shoot something like this you will most likely have to put standard bulbs back in to figure out if the LEDs are the cause. You should be going through a process of elimination, checking stuff off the list as you verify each step.

Because someone worked on it before you and you had electrical issues when you got it, you can't trust or assume anything that was done before you, to be correct. Removing all the affected bulbs, then testing to see if you still blow the fuse would let you know if the LEDs are the problem.

 

[Rickf]

There also may be an issue with the cluster's circuit board. You might try to unplug the cluster and see if the short still exists.

 

[Oldbear42]

I unplugged the plug that connects the rear lights. Fuse still blew which means it’s not causing the problem. Pulled the plug on the firewall that is responsible for headlights, front markers running lights etc and fuse didn’t blow. I’ve not touched the front light wiring on the truck so my guess is it’s either the front lights or something under the dash.

I just replaced the wiring from the firewall out (for rear lights and most of the front) as it was so full of clip-taps, melted and broken wires, missing wiring and even a few 110v marrettes. It was simpler than tracking and fixing all the issues.

 

[Notyushi]

This is the post creator’s brother. We discovered that someone had spliced a ground lead into the front indicator harness which was causing the fuse to blow. The problem I’m having now is power is simply finding a path to ground. The illumination pin on the dash has only 1-2 ohms of resistance to ground with the dash unplugged. The interior splice also has the same issue. We are also not getting power to the dash lights, wiper switch or anything else on the splice with the switch turned on.

 

[Jgonick]

We discovered that someone had spliced a ground lead into the front indicator harness

Glad you found it.

We are also not getting power to the dash lights, wiper switch or anything else on the splice with the switch turned on.

I have to ask- Did you twist the pull out light switch? twisting it controls brightness to dash etc..
and I'm assuming the fuse is good (PANEL LPS).

 

[justinbrugg]

Glad you found it.



I have to ask- Did you twist the pull out light switch? twisting it controls brightness to dash etc..
and I'm assuming the fuse is good (PANEL LPS).

We have. It’s a new light switch. The old one always worn.