Interior and tail lights not working.

[SayBye]

Bought a 91 4x4 long box the other day and the first thing I noticed is the tail lights and interior gauge lights, cab lights and heat/ac lights aren't working. All fuses inside the cab are good. Any ideas?

[87MJTIM]

Check the ground wires.  Dash ground is just above the park brake release handle.  Tail light ground is behind the drivers tail light.

 

See Cruiser's Renix Tips

 

(I know a 91 is not a Renix, but the ground refresh should apply)

[jimoshel]

A test light is invaluable in a situation like this. Get one and learn how to use it. I made one up using a light socket and bulb, 20 feet of wire, a little over kill but it works, and a test prod. Connect the clip to the negative post of the battery, more reliable than trying to find a good ground somewhere and use the prod to check for voltage at the sockets and connectors.

[Guest]

A test light is invaluable in a situation like this. Get one and learn how to use it. I made one up using a light socket and bulb, 20 feet of wire, a little over kill but it works, and a test prod. Connect the clip to the negative post of the battery, more reliable than trying to find a good ground somewhere and use the prod to check for voltage at the sockets and connectors.

Go one step further and get yourself a DMM (digital multi-meter); it'll more than pay for itself, trust me. Once you start chasing electrical gremlins, it's only a matter of time before you wind up needing one anyway.

 

Check the ground wires.  Dash ground is just above the park brake release handle.  Tail light ground is behind the drivers tail light.

 

See Cruiser's Renix Tips

 

(I know a 91 is not a Renix, but the ground refresh should apply)

^^^ As well. The culprit you'd be looking for under the dash is going to be above the parking brake release handle; should be a stubby little ground going to the bottom of the dash which you can beef up to give all the electronics inside the cab a better grounding point.

[gogmorgo]

If grounds don't work out, check the headlight switch. It's a known problem area.

The load from the headlights is a bit much for it, and it gets a bit melty after a while at the connector. Mine caught fire. There's a current thread about an upgrade headlight harness that'll solve this issue. It's a good idea whether or not the headlight switch is causing problems.