Hello,

I have a 1976 f-250 4x4 with a problem with the lights. Just started; when running lights are turned on the dash lights flicker off and on and the tail lights including breaklights will not work. I have replaced the headlight main switch along with both the hazard clicker and directional clicker. I do here a clicking under the dash that corresponds to the lights going on and off. The headlights work but will dim with each flicker. When the lights are not on the tail lights and break lights work fine. I checked my grounds on all of the lights. I do have a diagram of the wiring in my hayes book but it does not show the box located under the steeing weel behind the dash. It is bolted to a bracket that is bolted to the dash. The clicking may be coming from that. Is this a breaker for overload protection? Any suggestions would be great. Truck runs great otherwise.

Thank you

 

How did you check the grounds? Visually? Take a long piece of wire and hook it to the negative of the battery. Take a meter and hook one probe to the wire you hooked to the battery, and touch the other probe down beside the bulb so it touches the brass part of the bulb. Do this with the headlights on. If you get any voltage reading, your ground is not good. You could also go ahead and try to stuff the wire that is hooked to the neg of the battery, down in beside the bulb so it touches the brass part. Then see if that cures the problem on that side.

I am pretty sure you have a grounding problem, and it may be a major one. The ground return starts at the brass part of the bulb, goes through the contact in the side of the socket, goes out the bottom of the socket on a wire, and this wire is bolted to the bed somewhere. Since both sides are not working, I would tend to believe the whole bed is not grounded.

If you find that it is a grounding problem(the temp bat neg wire cures the problem), I would scrape some paint away on the bed and then the frame somewhere, and run a short jumper wire from the frame to the bed. I would then go up front and run a short ground wire from the frame up front to the battery neg or the engine block. I would also run a short wire from the engine block to the firewall. This may cure the clicking under the dash too.