Lights

[tsn98]

Hey everyone, I have an 87 half ton that i bought about two years ago. I never had any problems with any of the lights except the dash lights and the license plate marker lights. About a month ago, I finally fixed the dash lights which had not worked since I bought it. Once those were fixed, I took it for a drive at night but realized that when I turned my headlights on, none of the lights on the back of the truck (backup lights, tail lights and blinkers) or the cab lights work. The dash lights, head lights, front blinker and lights on the sides of the fenders all work perfectly fine. Anyone have a similar problem or know of a possible cause?
In addition i have my license plate marker lights wired in (I think correctly) but they don't work either. Any ideas? Thanks!

 

[J Knight]

Start with the simple stuff, check the fuses, unplug the bed harness from the frame harness at the end of the left frame rail and check for power with a test light.

 

[HotRodPC]

Are you sure these lights were working before the dash light repair? I'm thinking I'd start with the bed harness and a test light as John suggested. I don't think I'd go with the dash light repair and no bed lights working being a related issue. I'm thinking it 2 separate issues. Reason being, when you lose your dash lights due to a blown fuse, you also lose your park and marker lights. If dash lights are working, the fuse isn't blown. Sounds like all you've lost is all the lights that go to the rear of the truck so I think your problem is right there. Could even be the ground wire.

 

[tsn98]

check the fuses, unplug the bed harness from the frame harness at the end of the left frame rail and check for power with a test light.

Ill double check the fuses and then move onto the bed harness with a test light.

Are you sure these lights were working before the dash light repair? I'm thinking I'd start with the bed harness and a test light as John suggested. I don't think I'd go with the dash light repair and no bed lights working being a related issue. I'm thinking it 2 separate issues.

Im sure that these lights were working previous to the repair but you are right, they dont seem like theyd be connected. Thing that throws me is all these rear light work perfectly fine when the headlights are off, but as soon as you turn the headlights on, everything goes.

 

[HotRodPC]

I'd be checking the grounds on the headlights too. I've seen some weird things happen before with grounds. Like maybe the headlight grounds aren't good, and they're taking away the ground through the headlight switch and the rear lights.