Tail Light issue

[td87]

Ok so I am just about finishing up my k30 swap, and ran into a problem with the tail lights. Not sure where I went wrong because the only thing I did with the tail lights is disconnect them at the plug in the rear.

The front lights work just fine, the tail lights don't work. The brake light and turn signals work only when the light switch inside the cab is not pulled out. As soon as I go to pull the light switch on, the hazards dont work nor will the brake light. The license plate lights do work. I am at a loss after having screwed around with this issue all afternoon. Any input would be greatly appreciated, thanks

 

[J Knight]

You need to inspect the tail light harness, make sure there isnt a wire pinched or broke. Thats where I would start.

 

[td87]

is the tail light harness in the cab?

 

[J Knight]

The tail light harness runs from a plug(4wire) on the firewall down the drivers side frame rail to the plug you messed with.

 

[td87]

ok thanks, Tomorrow after work Ill hopefully find something out of the ordinary and fix it

 

[89Suburban]

You need a wire diagram....

 

[SlickGTP]

Make sure all the grounds are good too. I had issues until I realized that I had the bed insulated from the frame at the time I was testing stuff out. The taillights ground through the bed to the frame.

 

[MrMarty51]

Make sure all the grounds are good too. I had issues until I realized that I had the bed insulated from the frame at the time I was testing stuff out. The taillights ground through the bed to the frame.

Poor ground in lighting systems can cause some mighty weird problems.

 

[HotRodPC]

Make sure all the grounds are good too. I had issues until I realized that I had the bed insulated from the frame at the time I was testing stuff out. The taillights ground through the bed to the frame.

This will be my suggestion. You missed a ground somewhere, or a ground is corroded or something of that nature. To confirm that, just a test light aka Continuity tester. Ground it to the bumper or frame that you KNOW for fact is a good ground. Turn on the taillights, pull the bulb out of the socket and hit the Taillight filament button. If it lights up, then you KNOW it's a ground issue.

Best to even turn on the flashers too. Hit the other filament button, then 1 should flash, the other should light solid for tail lights. That way you're testing the circuit all the way out to the light socket.

 

[HotRodPC]

Another question, is this a new bed to you? You'd be surprised, but BOTH taillight bulbs just might be burned out too. Or, there was a short and it blew out or burned out both taillights. How about Dash lights? Dash lights are on the same circuit as tail lights. Are they working? If not, chances are a complete circuit problem, and could be that circuit.

I was diagnosing back up lights not working on my 84. Luckily I didn't spend a bunch of time on it, and realized, you know, 1 light could have gone out and never been replaced since people usually don't get to worried about BU lights, then maybe the other went out later on. Sure enough. Nothing wrong at all, just that both bulbs were burned out. Replaced bulbs, been working since.

 

[td87]

My bed right now is just sitting on the frame with 3" blocks and is not bolted down because I am waiting on some bolts to come in this Wednesday. So I am hoping this is whats causing my issue, what do you guys think?

 

[HotRodPC]

Could be. The bed may not be making a ground.

 

[89Suburban]

Do pickup beds from factory have a grounding strap?

 

[J Knight]

Well thats your problem, the bed needs to be bolted down to make ground.

 

[bucket]

When I put the step bed on my truck, I had to add a dedicated ground wire from the frame to bed so the lights would work right. In hindsight, it's probably because there were only 2 bolts holding the bed on at that time.