Tailights stopped working please help

My truck is becoming a problem vehicle. My tailights decided to stop working. Its a 78 Ford F100 Ranger. A couple weeks ago my tailights wernt on, then I hit a bump and they came on. Next day they wouldnt work and they havnt worked since, its been a couple weeks and thats a problem because I leave work when its dark and this is my only vehicle to drive at the moment. I checked to make sure there were no broken wires, and as far as I can tell theyre all good for being 30some years old. I also changed the headlight switch thinking that was the problem. My dash lights were always dim, and when the tailights completely stopped working so did my dash lights. I noticed the license plate light isnt working either and I'm wondering if that bulb went out, could that be the problem? I dont know if the bulb is bad or if its just not working because the tailights wont. I know the bulbs are good in the tailights are good because they come on when I press the brakes. If you have any ideas please let me know, its fairly urgent as driving the truck at night is not optional.

... My dash lights were always dim, and when the tailights completely stopped working so did my dash lights. I noticed the license plate light isnt working either and I'm wondering if that bulb went out, could that be the problem? I dont know if the bulb is bad or if its just not working because the tailights wont. I know the bulbs are good in the tailights are good because they come on when I press the brakes. If you have any ideas please let me know, its fairly urgent as driving the truck at night is not optional.
Ok, so what you're saying is the brake lights and turn signal lights work but not the running lights or dash lights or license plate light. (they are all on the same circuit) And they can go on and off when hitting a bump. Correct? If so, it is possible it's your headlight switch but you say you replaced it with no help. Correct? If not, check the switch. If correct, I'd look at the fuse box. First, replace the fuse. Even if it doesn't look burned out. They can be bad and still look good. Next, using a test light, check the fuse box for power getting to the fuse. It's possible a wire has become disconnected or even broken off on the back side of the box. You may have to remove the fuse box to take a look. If there is power, check to see if there's power getting to the headlight switch. Could be the wire going to the headlight switch has become disconnected or broken off on the fuse box end. Also possible it's got a bad wire so check for power at the headlight switch end too. If all that checks out, power getting too the light switch, then the problem has to be between the light switch and the tail lights. Not too likely there but let's see what you find first. Hopefully it's a simple fix. Good luck :)

I was thinking it had to be a fuse. Only problem is its not the original box so I'll have to replace all of them because the guy that put it in wasn't nice enough to label anything. I also have another aftermarket box under the hood so I'll have to check that one out as well. Hopefully it's not a power issue to the fuse box because I don't have anything to test power and am strapped for cash at the moment. My project tomorrow will be replacing fuses and praying that works. Good to know it's not something I never heard of, that's what I was worried about.

Fuse box has already been replaced huh. If it's an aftermarket fuse box (most likely) all the wires plug into it with crimp on connectors. If so, a wire could have easily become unplugged so check to make sure they're all still pushed onto the spade terminals. Good idea to replace the fuses one at a time first. You never know, you might get lucky.

All fuses replaced and nothing. I broke down and bought a tester, the fuse box is good, all fuses have power to and from. So it has to be something between the fuse box and the tailights. What components are in between other than the headlight switch? I know its not the second fuse box under the hood, I traced all of those wires and they all go directly to engine components, nothing under the dash or leading to lights.

All fuses replaced and nothing. I broke down and bought a tester, the fuse box is good, all fuses have power to and from. So it has to be something between the fuse box and the tail lights. What components are in between other than the headlight switch? I know its not the second fuse box under the hood, I traced all of those wires and they all go directly to engine components, nothing under the dash or leading to lights.
Ok, on a factory fuse box it goes from the fuse box to the headlight switch. Then, from the headlight switch to the tail lights/dash lights/ license plate lights, anything else that comes on when you turn on the headlight switch. I'd check from the fuse box to the headlight switch next. Use your test light (great you bought one, very, very useful tool) to make sure power is getting thru the wires. Also check the wire connector at the headlight switch for broken/burned wires/dirty connection, anything that doesn't look right, etc. Hopefully the problem will be there and an easy fix. Hang in there, you'll get it! :smile:

Good news ish. I pulled all the gauges out and started tracing wires with the tester. There is a baseball sized mangle of wire and electric tape between the headlight switch and the gauge cluster . Somewhere in there is a loose wire. Just moving it a tiny bit got all lights working again. I'm going to take all the tape off and find the bad wire in there. It's going to take a while because there's 3 t''s from the harness all collecting there. I know it's there, now I just gotta find it. Thank you for all the help. Your keeping this truck on the road

Good news ish. I pulled all the gauges out and started tracing wires with the tester. There is a baseball sized mangle of wire and electric tape between the headlight switch and the gauge cluster . Somewhere in there is a loose wire. Just moving it a tiny bit got all lights working again. I'm going to take all the tape off and find the bad wire in there. It's going to take a while because there's 3 t''s from the harness all collecting there. I know it's there, now I just gotta find it. Thank you for all the help. Your keeping this truck on the road
Actually, that's a good thing. As per our other post, the PO is to blame. Glad it was easy. Not fun but it could have been worse. Party for you tonight!!!