Lights out.

[n33k0]

My list of things that need fixing on the truck is getting longer every day, but I have an issue now that has me scratching my head.

The lights inside the cab of my 1972 C10 have stopped working. One night, everything worked fine, the next night none of the gauge lights nor the dome light will turn on. I had recently replaced all the bulbs in the instrument panel and they had been working fine for a few days. Now the only lights that work in the cab are the turn signal indicators. Luckily, none of the exterior lights are affected, so I can still drive at night, I just can't see my gauges (unless I drive under a streetlight )

I checked the PNL LTS fuse (panel lights?) and it was ok. I had slammed the door pretty hard right before noticing the lights were not working, and my first thought was that I knocked a wire loose, but I can't see anything out of place in the tangled mess under the dash. Any ideas where to start troubleshooting?

Thanks in advance
-Nick

[ole dollor]

could be rusty fuse holder, or a bad headlight switch. might start there. good luck.

[Steeveedee]

Slammed the door? Temper, temper! J/K, it sounds like the rheostat in your headlight switch may be bad. Rotate it all the way counterclockwise until it clicks and see what happens. They should come on all the way bright. If that is the case, you will need to replace the headlight switch.

[GuyO]

It does sound like the headlight switch reostat. I spray electrical contact cleaner into the switch through the knob rod hole. Also, some dash bulbs are loose in the holders, a shock from a door slam may have knocked a few out. I bend the bulb wires out to better grip the holders. My .02. G.

[n33k0]

Thanks for the ideas, guys. It's not so much my temper that has me slamming doors, it's the weather seal! With all the windows up the doors need a good bit of force to latch properly, but that time the windows were down and I threw the door thinking they were up.

Would one loose bulb stop the rest of the interior lights from functioning properly? I haven't checked them all, but the two that I did pull were snug in their clips.

I checked the fuse box, replaced the fuse for good measure, cleaned out the switch with electrical cleaner, removed the switch to clean the wire contacts in the plug... still no good. I guess the next step is to buy a new switch. Is it normal for these switches to go bad with time?

[ole dollor]

Originally Posted by n33k0

Thanks for the ideas, guys. It's not so much my temper that has me slamming doors, it's the weather seal! With all the windows up the doors need a good bit of force to latch properly, but that time the windows were down and I threw the door thinking they were up.

Would one loose bulb stop the rest of the interior lights from functioning properly? I haven't checked them all, but the two that I did pull were snug in their clips.

I checked the fuse box, replaced the fuse for good measure, cleaned out the switch with electrical cleaner, removed the switch to clean the wire contacts in the plug... still no good. I guess the next step is to buy a new switch. Is it normal for these switches to go bad with time?

one bulb would not cause the others not work, and the head light switch can go bad any time. I do not know if yours has ever been replaced, if not it may be time, also the plugin on the back of the gage cluster is another place to check, it could be dirty or loose , turn the lights on and wiggle the connector and see if the lights come on are blink a little...hope you find the problem...good luck.

[VetteVet]

To quick check the lights apply a 12 volt jumper to the pnl lts fuse and watch for the lights to come on. The head light switch does not need to be on. If the lights come on the problem is power from the switch to the Pnl Lts fuse. If you check for power at the pnl Lts fuse and have 12 volts with the headlight switch on then the problem is after the fuse and in the wiring or in the cluster.

[n33k0]

Originally Posted by VetteVet

To quick check the lights apply a 12 volt jumper to the pnl lts fuse and watch for the lights to come on. The head light switch does not need to be on. If the lights come on the problem is power from the switch to the Pnl Lts fuse. If you check for power at the pnl Lts fuse and have 12 volts with the headlight switch on then the problem is after the fuse and in the wiring or in the cluster.

I checked the voltage at the fuse block and didn't get any reading from any of the fuses. All the electrical systems work, except for the interior lights, but I still get a reading of 0 volts from every fuse I test in the fuse block. I touch the voltmeter leads to the metal caps of the fuse, maybe I'm doing it wrong? I'm not exactly sure how to test the lights with a 12 volt jumper

I've always had a hard time wrapping my head around electrical issues.

I was going to simply replace the switch, but after the volt test I'd like to rule out a faulty fuse block before I buy a switch I don't need.

[n33k0]

I bought a new headlight switch but it has not solved my problem. It's actually gotten worse, now my brake lights, hazard lights, and running lights have stopped working, too. Headlights and blinkers are fine. I can get the gauge and running lights to work by using a spare wire to connect the red power wire to the gauge and running light sockets on the plug, but I can't get the dome light to turn on using this method... when the switch is plugged in they all stop working again. What are the chances that the switch is bad right out of the box?

[boynton]

fairly low but it does happen. i would check over the work you have done recently and make sure you don't have an issue there. Next I would start looking at your fuse panel and make sure you don't have any loose connections or grounds (there are several throughout your truck. I would also eliminate any unused wires roaming around under your dash as these could be hot wires grounding causing issues or your fuse panel to short out. Unfortunately there is no one size fits all for a wiring problem especially when there has been modification to the stock wiring.

[n33k0]

The wiring on the truck is a mess, I guess it's time to stop putting off that clean-up project. I'd love to start from scratch with a new wiring kit, but that is out of my budget at the moment.

In the meantime, is there a test I can do to ensure the switch is functioning? I can get most of the lights working if I bypass the switch, but the switch still works to operate the headlights. If I can avoid buying another $20 switch and get the truck on the road in time for tailgating at the game this weekend, that would be wonderful.