No dash lights

[BigBlueBowtie]

Howdy, I got an 81 k20 that’s having some electrical problems. The dash lights/all interior lights and tail lights are out. I’ve checked the fuse, ground and replaced the headlight switch. Still don’t work. Any help would be greatly appreciated.
Thanks!

 

[Jgonick]

What fuse did you check? TL/CTSY or INST/LPS or both?

Does your horn & dome light work?
Do your headlights work?

 

[BigBlueBowtie]

I’m not near my truck right now so I pulled a pic from the internet. I circled the one I checked. The horn hasn’t worked since I’ve had the truck. Haven’t put a tester on the dome light but the floorboard light isn’t working. Headlights are working.

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[RustyPile]

The fuse you checked is for the gauges, not the lights you're talking about. The dash lights and tail lights are on the same circuit, In addition to the tail light fuse, the dash lights have a separate fuse. The power for the dash lights come from the tail light circuit.. The dash light fuse can blow and the tail lights will continue to work.. If the tail light fuse blows, both sets of lights will go out.

[EDIT----I MADE AN ERROR IN THIS POST.. THE orn-40 CIRCUIT ALSO FEEDS THE TAIL LIGHT CIRCUIT FROM THE FUSE BOX TO THE HEADLIGHT SWITCH.] The courtesy lights and dome light are on a circuit together, and could be connected to the cigarette lighter circuit/fuse.. For starters, check ALL the fuses first...

I see a wire (black?) that has a scotch-loc connector on it.. That's a NO-NO, not installed by the factory.. If the splice is necessary, it should be made in a proper manner..

 

[BigBlueBowtie]

Thanks bud, I’ll take a look at all the fuses. It’s not my fuse box, I got it off the internet.

 

[Jgonick]

Hopefully just the tail light fuse. That would affect the tail lights, courtesy lamp(floorboard) and dash lights. Usually the horn & dome light are on another circuit. Both those circuits are fed by the same red wire coming from engine compartment.That's why I asked the questions I did- I was running down the possible problem area.

 

[RustyPile]

Hopefully just the tail light fuse. That would affect the tail lights, courtesy lamp and dash lights. Usually the horn & dome light are on another circuit. That's why I asked the questions I did- I was running down the possible problem area.

Not to beleaguer the point but the courtesy lights are probably not on the circuit with neither the tail lights or dash lights.. Depending on the model year, the stop lights could be on the same circuit with courtesy lights. He has an aftermarket fuse box and possible wiring harness, so all bets are off as to what is connected with what.. I agree with you on the blown tail light fuse.. I'm convinced he has another blown fuse also. The causes of the blown fuses remain to be known.

 

[RustyPile]

Thanks bud, I’ll take a look at all the fuses. It’s not my fuse box, I got it off the internet.

Harley, I made a mistake in my suggestion.. Jgonick followed my sage advice and referenced an up-to-date diagram and he and I had a discussion about it.. The orn40 circuit does indeed, provide power from the tail light fuse for the tail lights.. it continues on from the headlight switch to the courtesy lights..

Check for power on both terminals of the tail light fuse. You should have power on both sides.. Power on 1 side only indicates a blown fuse.. No power on either side indicates an open circuit feeding that section of the fuse box..

 

[BigBlueBowtie]

Hey bud, just got the chance to check all the fuses. The taillight fuse was the only one blown and I replaced it, it’s still not working.

 

[Jgonick]

Did it blow the fuse again? If not- check for volts at the fuse. If you do have volts there, next check the orange wire at the light switch connector.
If it blew the fuse again, you have a short somewhere.
Replace the fuse, does it blow the fuse again immediately?
If not remove the fuse from the INST LP then pull the light switch out one notch- did that blow the fuse?
If so -I would start by looking at your tail lights, front turn signals,and side lamps for a short. Specifically the brown wire. possibly bad socket etc.. Also if you have a trailer plug, check the brown wire where they possibly spliced it to run to the plug. & the license plate light


Were the lights previously working then just stopped working one day? Had you worked on the truck recently before they stopped working?

updated post- to try to narrow the problem down.

 

[BigBlueBowtie]

Hey bud, the fuse didn’t blow and it’s getting around 14.5V. I checked the orange wire at the switch and was getting 23.7mV.

 

[BigBlueBowtie]

Hey bud, the fuse didn’t blow and it’s getting around 14.5v. I checked the orange wire at the switch and was getting 23.7mV.
I was driving down the road and all of my dash lights just stopped working, didn’t realize that tail lights weren’t working until a couple nights later.

 

[Jgonick]

You should be getting roughly 12v on the orange wire at the switch. Does your courtesy (floor) light work? Did it work before? making sure the bulb isn't burned out. Follow RusyPile's advice about checking both sides of fuse.


Edited to remove unhelpful advice at this point.

 

[RustyPile]

Hey bud, the fuse didn’t blow and it’s getting around 14.5v. I checked the orange wire at the switch and was getting 23.7mV.
I was driving down the road and all of my dash lights just stopped working, didn’t realize that tail lights weren’t working until a couple nights later.

23.7 mV is nothing. Did you check both sides of the fuse?? You can check this with the fuse installed. There are 2 metal "tabs" visible on the fuse on each side of the fuse rating number. Voltage on only one side means the fuse is blown. If you have voltage on both sides, look for a loose or open connection on the wire between the fuse box and headlight switch...

 

[Ricko1966]

And remember @BigBlueBowtie there is no such thing as just a blown fuse,fuses blow for a reason and until the cause is found an d repaired the problem will come back.