Bram

HELP! I had my headlight switch burn out the other night and by the time I got home I had nothing but headlights. No dash lights, no running lights, no hazards, nothing.
I replaced the headlight switch and wiring harness that connects to the switch, and also put in a headlight wiring harness with relays connected to the batteries to take some of the load off the switch.
Well after getting everything wired I tested it.
1. I now have lights working on everything but the bed.
2. Also if I turn the headlights on the trailer brake controller light turns on?
3. Tested it at night and found if I press the brake pedal the bed lights come on very dimly???
4. If I turn the hazards on they start blinking the radio and, blink really fast outside and then slow way, way down.
I bought another new light switch and tried that and, the same thing. Disconnected the trailer break controller, no change.
Checked all fuses and relays and all are good.

Help... I have no tail lights no brake lights, any suggestions?

Robert Rausch

Putting in the relays was a good thing to do. I've been running my truck like that for 10 years, and I've never had a headlight switch even get warm.

I would use a test light--the kind with a sharp probe--and try to trace the path of the tail light and brake light wires and see if they haven't shorted out somewhere along the way. It all the wires checked out, personally I'd take it to somebody who could run some diagnostics on the PCM, ECM etc.

Bram

Thanks Robert, I noticed that when I stick a test light on each wire on the back of the new switch I get a light on all wires except for two wires, the light blue and the blue black are dead? I have know idea what these two wires go to? Everything else under the bed is dead. If I turn the hazards on though it blinks all the lights on the bed, and if I push the brake on, it lights the bed up.

nickg

sounds like a ground is poor, maybe visit the headlight switch again and check to see that none of the wires are burned or are broken inside the plastic sheathing

Bram

The ground part is what I've been really looking at, so far everything is fine.

GAmes

I suggest you drop the few dollars that a factory service manual costs. Chasing sparks is a lot easier with a diagram.

Robert Rausch

Ditto that. The factory wiring diagrams are extensive and are needed for any detailed trouble shooting of most electrical items on our trucks.

Junk Man

Check pdftown 1st.

Bram

The service manual was the first thing I grabbed when I started trouble shooting.
I have sneaking suspicion that it's a ground problem but can't find it yet.

One thing I failed to mention is that this is not the factory bed but, is a Bradford Built bed.

Bram

Well I found the culprit! There were two wires under the the flat bed in the wiring harness bundle, one was broken, the other (ground wire) was nearly broken.
Repaired everything and now it's working as it should be.
Thank you all for the help.