Instrument Panel Lights Staying on When Truck is Off

[ole Buckskin]

Hello,

I’ve installed a new wiring harness on my 1980 c10. It’s one of those universal GM harnesses. I have everything hooked up and working, except that the instrument panel lights stay on even when the truck is off. The headlight switch is working fine — the headlights and taillights come on/off when the knob is pulled out/in, and the dimmer works on the headlights, but I can’t figure out what’s causing the instrument lights to always stay on. I have the IP lights (gray wire) fed to the fuse box, which connects to the feed wire (green) to the headlight switch. The IP lights do turn off when I pull the fuse. There’s no weird splices or anything, it should be a clean circuit from switch to fuse to lights. I’ve also verified that the connections are fine at the instrument panel and the printed circuit appears fine as well.

I appreciate any ideas or suggestions, thanks!

 

[DoubleDingo]

Painless? American Auto Wire? Some other brand? You may want to contact the manufacturer of the harness and ask them about it.

 

[dsteelejr]

If you can, pull the fuse block off and look at the back side to see where the fuse slot for the gray wire is getting its power from. Maybe someone built the harness on a Monday or Friday. I agree with @DoubleDingo, call the manufacturer.

If it’s too much hassle since you already have it installed you could splice the green feed wire to the gray wire and run an inline fuse in between.

It’s a lousy time to find out something is wrong with the harness.

 

[Matt69olds]

Unplug the headlight switch. If the dash lights go out, the headlight switch is powering the lights when it shouldn’t.

I’d call the manufacturer first, maybe they have some other ideas.

 

[dsteelejr]

Unplug the headlight switch. If the dash lights go out, the headlight switch is powering the lights when it shouldn’t.

I’d call the manufacturer first, maybe they have some other ideas.

He said the lights don’t turn off even when pulling the fuse. Sounds like the fuse block was wired wrong.

 

[ole Buckskin]

Hey everyone,

I appreciate the ideas! The harness is one of those universal ones from eBay, not sure who the manufacturer is, I’ll have to check later. The lights do turn off when I pull the fuse, which is confusing why they don’t switch on/off with the headlight switch.

I’ll try testing if the lights turn off by unplugging the head light switch.

If worst comes to worst, I may just do an inline fuse and splice from the taillights to the gray wire/ IP lights. The taillights are working at the headlight switch.

 

[dsteelejr]

Hey everyone,

I appreciate the ideas! The harness is one of those universal ones from eBay, not sure who the manufacturer is, I’ll have to check later. The lights do turn off when I pull the fuse, which is confusing why they don’t switch on/off with the headlight switch.

I’ll try testing if the lights turn off by unplugging the head light switch.

If worst comes to worst, I may just do an inline fuse and splice from the taillights to the gray wire/ IP lights. The taillights are working at the headlight switch.

Read that wrong. My bad.

 

[WP29P4A]

A common cause for what you described would be tying the dash lights to the radio wiring, and getting the three powers sources mixed up.(Or tied together) Radio has full time 12 volts for clock in radio, also 12 volts from accessory, and 12 volts from dash lights when headlight switch is activated. It is one of the easiest ways to create a situation like yours.

Might not be your problem, but I have seen it and thought I would toss it out there. Accidentally tying two circuits together often causes odd issues that are hard to locate, with real strange symptoms. Putting single element bulbs in dual element sockets can also tie multiple circuits together and cause wacky results.