I just bought a 84 f150 4x4. When I first got it (yesterday) the left tail brake light was always on, blinker didnt work. Right side is fine. I figured light bulb was out so I replaced it. That didnt fix it so I began tracing wires. Right under the bed the po had spliced new wireing in I guess to replaice a tail light assembly. The wires and splices looked fine except for one black wire that was striped and the bare copper was wraped around part of the frame
So I cut it, put on a loop connecter and screwed it to the frame after I scraped the crud away to get good contact.
Now everything is fine and dandy the way it ought to be except for when I turn on the headlights. The taillights come on, the blinker works, the brake light works, but when you get on the brakes with the blinker on the whole thing shuts down. No lights at all in the left taillight. This only happens with the headlights on. With them off it all works as it should.
I'm guessing there's a short somewhere, does that sound right? The portion of wire I was able to trace looked good, as did things at the fuse box.
Any ideas or suggestions what to do and where to look next?


I hate electrical work. The parts are too small and you never get greasy enough.

Thanx yall!

 

This is only a WAG but maybe the wire is too small to handle the load, especially the ground wire????

One or two circuits running and it struggles along OK, three circuits with headlights, turn and brake and "poof", dead?

Lee

 

Possible, but the wire is the same size as what's in the factory wire bundle.

The fact that there is a ground there kinda makes me wonder too. I doubt the factory grounded that wire on the frame, and it comes from up front somewhere. Why would a ground wire be ran all the way back to the end of the bed just to be grounded? Doesnt make sence. Should that wire be ran into the tail light assembly and grounded in there somewhere?

Idunno, maybe I'll just fork out the $ and buy a whole new taillight assembly and re do it all myself. That's the only thing keeping me from a new inspection sticker.

 

Here's something to try. Take a battery sized cable, and purchase a grounding post as well, and run all grounds from your lights to the single grounding post. Use a 10 gauge wire for grounding from all lights, and add an aftermarket RFI resistor to your radio and alternator. This works for fiberglass bodied vehicals, and you'll notice your lights get a lot brighter, and the load on your alternator drops significantly. A body ground is fine when a truck is new, but it has to ground through a lot of rusted metal after the truck is old. Did this to my 69, and the electrical took on a whole new life, with a lot less problems.