ok couple of wiring problems im havin with my 78 f250, which are both driving me insane, no interior dash lights works, and the fuel guage stopped working recently (its definitely electrical sending unit, float, etc are all fine) anyone have some advice on either? ive checked fuses and everything seems to be fine

 

For the fuel gauge;

Take the wire off the sending unit at the tank, and with the key in run, engine off, take the wire and ground it. The fuel gauge should swing full scale in one direction. Then take the wire off ground and let it hang in the air. The guage should swing full scale in the opposite direction. If it passes this test, the gauge and the wiring are good, and there is still something wrong with the sending unit.

Turn your headlight switch all the way to the left till it finds the detent. Does your interior light work? If not, have you checked the bulb?

 

ok ill give that try in a little bit with the fuel guage, and ya i know what you mena about turning the headlights switch, but that doesnt work either, and the bulbs shold be fine because i checked the wires and there not even getting power, about a month ago the heat/defrost panel light worked, and sometimes the one behind the headlight and wiper panel, but not the guage lights, now none of them work.

 

oh and im pretty sure the dome light doesnt work either, so idk if one problem is tied into all of them or what

 

Sorry, I miss-read your post. Your dash lights don't work. The power for these comes from the headlight switch. Find the dash light fuse and get a meter or testlight. Turn the headlights on, and then probe BOTH sides of the dash light fuse. If you do not have power on either side of the dash light fuse, then I suspect your headlight switch is bad(the part that dims the lights).

 

any idea what the fuse would be labeled as, cuz i honestly couldn't find a fuse for that. i checked but i couldnt figure out which one would even go to that

 

A lot of times it's called "inst" for instrument lights. It will be small, something like 3 amp.

 

ok yup i know what your talkin about, i actually got lucky last night and just fooler around with it some more and got the lights working, i dont rly know what i did to be honest with you maybe just some bad connections, and i did that trick for the fuel guage and it worked so must be the sending unit! which is good i really didnt feel like going through all that wiring.