No Lights

[Ruby38779]

Heyo, I'm Ruby, I'm fairly new here, and I've already got a question.

 

So basically I've got a 81' 720 that for some reason lost its tail lights, brake lights, running lights, and turn signals just from sitting in my parking space, I've got no idea how and I already messed with the hazard switch to see if it was that, my only guess is the cold maybe? any help would be appreciated! 

[datzenmike]

Do the dash lights, turn signals and running/marker lights work at the front????? If yes (and no brake lights at the rear) I would say the ground is now bad at the rear. Diagrammatically the Black ground wire is about where the license plate is, perhaps bolted to the bumper? The black ground wire also goes back into the harness and to the front of the truck. The wire harness across the rear, plugs into the harness from the front on the right rear end of the frame roughly behind the RR tail lights. It's a round 6 wire plastic plug. Try unplugging and plugging it in several times to clean and make good contact. None of the lights will work without the common Black ground wire properly grounded..

 

Everything back there gets hit with rocks, salt, freezing slush and whatever. You might have a 15 pound iceberg hanging on the wires. I've driven in Ontario winters I know what's possible.

[Ruby38779]

4 hours ago, datzenmike said:

Do the dash lights, turn signals and running/marker lights work at the front????? If yes (and no brake lights at the rear) I would say the ground is now bad at the rear. Diagrammatically the Black ground wire is about where the license plate is, perhaps bolted to the bumper? The black ground wire also goes back into the harness and to the front of the truck. The wire harness across the rear, plugs into the harness from the front on the right rear end of the frame roughly behind the RR tail lights. It's a round 6 wire plastic plug. Try unplugging and plugging it in several times to clean and make good contact. None of the lights will work without the common Black ground wire properly grounded..

 

Everything back there gets hit with rocks, salt, freezing slush and whatever. You might have a 15 pound iceberg hanging on the wires. I've driven in Ontario winters I know what's possible.

They don't work in the front either, but I'll try that rear ground bolt and plugs, I'll be keep you guys updated if it works or doesn't, thanks!

[datzenmike]

I assume the dash lights are also not working?

 

The running lights are powered from the headlight switch. The brake lights are powered separately so having two things not working is likely something common like the ground. The front lights have their own ground at the front so again unlikely more than one ground is at fault.

 

 

 

Lets try to get the brake lights working. Get or buy a $5 circuit tester like this...

 

 

Brake and turn signals are powered from the 12th fuse over from the lefty side of the fuse box. Clip the tester to a good ground and touch both sides f the fuse and the light should light on both. If not the 15 amp fuse is bad. If ok then go to the brake pedal and test that the power is there on the Yellow/Red wire and on the Yellow/Blue when the pedal is depressed.

 

 

Running lights...

 

Check the 13th fuse from the left for power. If ok try turning the headlight switch on off on off multiple times. They tend to act up with age and the grease collects dirt. Cold makes the grease thick.

 

 

 

[Stinky]

The:

Tail

Turn

Parking

Head

Lights all go through the turn-signal/multi switch.  AFAIK....the brake lights do not share any of those circuits and do not have anything to do w/the switch.

 

Each one has its own connection in the switch....other than tail, dash, and parking (amber lights in front) which share a connection.

 

I don't think the switch is the problem.

 

As mentioned...fuses and grounds are more likely the cause.

 

I have not idea where the grounds would be.

[Ruby38779]

On 1/22/2023 at 8:43 AM, datzenmike said:

I assume the dash lights are also not working?

 

The running lights are powered from the headlight switch. The brake lights are powered separately so having two things not working is likely something common like the ground. The front lights have their own ground at the front so again unlikely more than one ground is at fault.

 

 

 

Lets try to get the brake lights working. Get or buy a $5 circuit tester like this...

 

 

Brake and turn signals are powered from the 12th fuse over from the lefty side of the fuse box. Clip the tester to a good ground and touch both sides f the fuse and the light should light on both. If not the 15 amp fuse is bad. If ok then go to the brake pedal and test that the power is there on the Yellow/Red wire and on the Yellow/Blue when the pedal is depressed.

 

 

Running lights...

 

Check the 13th fuse from the left for power. If ok try turning the headlight switch on off on off multiple times. They tend to act up with age and the grease collects dirt. Cold makes the grease thick.

 

 

 

Sorry for the late response, its been cold as hell outside and its just warmed up enough to work on the truck, I did look at and clean the plug near the rear and nothing changed, so I'll check the fuse box and tail light connections like you said, thanks!

[datzenmike]

I've been through N Dakota in the winter, I know cold.