Tail Light/Brake Light help

[RiverCityDave]

ok kids, my tail lights stopped working sometime in the last few weeks. 2 weeks ago a friend told me I had a tail light out, I couldn’t replicate the issue. Two days ago, I was in the field and had the wife take the truck in for inspection, and it passed with flying colors save for inop tailights. I pulled the back cargo panels tonight, and of course found some wonky splices for a trailer taillight controller, which I removed. They were crappy blade type splices, not weatherproofed at all, still they must have worked pretty well, the truck is 24 years old. Anyway, I still have no tail lights at all, regardless of the headlight status, but when the headlights are off, and I press the brake pedal, the brake lights illuminate very dimly, however so do the rear marker lights.

Any thoughts? I’m leaning toward a ground problem, but I haven’t done any voltage checking yet to see numbers, I’m just looking for some smart ideas.

 

[brettwilm]

Hi mellowdave, I have had that exact (I mean exact) same issue. First on the right side, and then on both sides. For me it turned out to be a ground short in the taillight housing. This is the white wire going separately to the side of the taillight/brakelight housing. It goes up through the black plastic and is supposed to be grounded to the metal side of the taillight housing. If it pulls away (at all), you lose the circuit. Test by stuffing anything that will close the circuit down in there between the metal side and where you see the copper wire. With the light switch on, the taillights should come on, and you can have someone step on the brake to confirm the brakelight filament illuminates.

Best way to ensure that ground is to solder it.

 

[RiverCityDave]

I figured I’d follow this up for posterity. BL up front - @brettwilm was right.

I went into the wiring diagram, cleaned all the grounds and still had the problem. Bending some tabs in the tail light harness itself resulted in changes, but also some broken tabs, so I ordered up two new (left and right) harnesses and problem solved. Been five years with no recurrence. Hope this helps the next guy.

 

[Malleus]

Those pigtails are the worst.