The Stovebolt Site Forums The Shop Area The Electrical Bay lighting help needed

I have rewired all lights on the rear of my truck ('70 C10) using the wiring diagram in the factory assembly manual. The signal lights work, brake lights work and the license light works. The tailights and rear side markers don't. I have checked everything with a test light and it all checks out. I have switched the bulbs to the front and they are fine. What is the problem?

Could it be the tail light wire just goes to the licence light. It needs to junction & go to each tail light. If you have current to the tail lights the trouble will have to be bad grounds or defective sockets.

The wire splits off and goes to each tail light and both sockets have current.

I just recently put the bed back on the truck. The frame has been painted as well as the bed and the light brackets. Everything was painted as seperate pieces.

Could it be that the bed isn't getting grounded to the frame because of the paint?

If it is a ground problem, why do the turn signals work and nothing else does?

bigbassmann,

I am not familiar with a '70 C10, but I looked at your rig in the gallery. Yours appears to be a step-side, so you have individual lights bolted to the bed...right.

You said you are measuring voltage at each of the tail light sockets. Where were you grounding your meter or test light to get a ground for your reading?

What would happen if you signaled a left turn, which you said works, used your meter to confirm the blinking voltage, and NOT moving your ground, test the tail light socket...using the same ground. If it proves good, technically the lamp should work when you stick it in.

If any doubt exists as to the quality of ground for the light assembly, you can use a little patch cord clamped to a good clean spot on the frame and a good clean spot on the light.

I wonder if the little solder button for the taillight could have paint covering it. Scratch around some more with your meter.

Stuart

Just for grins, check to see if the license plate light or dash lights blink dimly when the turn signals flash. It may have to be dark in order to tell.

Stuart, it is a stepside. I am grounding the test light to the frame rail and both contacts in the socket are clean and both show voltage. That is what has me stumped.

Hold the show. Guys, I just went out to check things in the dark. I believe I have some bad connections somewhere. I cranked the truck and turned on the headlights. The rear sidemarkers are coming on now but they seem to "flash" with the vibration of the truck. When I shut off the engine they burn without the "flash". The rear tail lights still do not work. The brake lights work, but only with the headlights off. The left turn signal worked until I pulled the headlight switch, then it quit working. The right signal works fine. I shut off the headlights and the left signal started working again. Pulled the headlight switch and the left signal continued to work. Some weird stuff is happening here. Guess I will have to start all over with this wiring thing and make sure all connections are perfect. Thought I was doing a good job the first time but now it seems otherwise.

Man, this electrical stuff gets me pi**ed off.

You probably don't have to rewire anything, just make sure you have good grounds to all of the fixtures. Try running a wire from the frame to each socket where you are having a problem. If that light works then you have a bad connection between the frame, bed, fender, light fixture, etc. Paint will not conduct sufficient current.

Sounds like a grounding problem to me, too.

Here's anaother voice in the choir...check all of your grounds. I had to run a dedicated ground wire to each light, solder it to the socket and then connect it to the frame with a small bolt. I could never find a reliable ground through the sheetmetal.

Still having problems. The taillights and rear side markers work occasionly but not like they should. They ficker on and off or don't come on at all. I tried running a ground to the left socket but all it did was make the tail light so bright that it makes it hard to see the turn signal flashing.

Just out of curiosity I put my test light clip on the frame and touched the other end to a bare spot on the bed. It lit up. Got to looking around and saw some flickering at metal to metal contact. There is a bracket on the left rear side of the bed where the license plate used to mount. It was barely touching the rear bumper brace and as the truck vibrated from the engine running, it was causing a spark where these two pieces were making contact. Every time they sparked the lights would flicker. If I pushed down on the bed the lights brighted up just like they did with the ground wire.

I figured there has to be a bare wire somewhere along the frame that is touching and causing the short. I tracked the wires along the frame paying close attention to where they went into each clip. Nothing. I couldn't find anything wrong.

My next thought was maybe one of the light sockets on the back was causing the problem so I unplugged each wire one by one and checked with the test light from frame to bed. After all wires were unplugged (no sockets hooked up), the test light still comes on. The test light only comes on with the headlight switch pulled to the on position. Headlight switch off, the test light goes off.

This has got me completely confused. I have no problem with any of the front lights. Headlights, parklights, turn signals and side markers all work fine. Just can't get the back lights to cooperate.

Any thoughts?

Clean a spot down to shiny metal on the frame & on the bed & install a ground strap. Brian

Ralph,

If you power your lights, and they have no way to get back to ground to complete the circuit, they won't work. When you put your test light on the frame (grounded) and touched the bed (hot), you completed the circuit and the little tester lit up.

Current flows from the battery through the wires to the lamps. Then through the filaments, which glow, and then back to ground...if looks like the bed isn't connected well enough to the frame to complete this path to ground.

If you do as Brain and others have suggested, you will probably solve your problem.

I think this is how it works.

Stuart

This sounds like you have the lights wired wrong. The bright filament should be the brake/turn signal and the dim filament should be tail light.

As several other people have said but you haven't caught on yet, GROUND THE BED TO THE FRAME. GROUND THE CAB TO THE FRAME. GROUND THE ENGINE TO THE FRAME. GROUND THE NEGATIVE TERMINAL OF THE BATTERY TO THE ENGINE.

Cletis,
The lights are not wired wrong. As stated, I used the assembly manual to get the wiring diagram and I confirmed that each wire was what the manual stated before I rewired. I have also triple checked (actually more like a dozen times) to make sure I wasn't wrong somewhere. By the way, I HAVE CAUGHT ON. I didn't mention it but, I have tried the ground from the bed to the frame with no results. Guess I will try that again to see what happens.

Thanks for all responses. Even you Cletis.

Check your GROUNDS... :p

bigbassman,

You are frustrated with your lighting and Cletis is frustrated that you don't appear to understand the importance of grounding.

Every thing you said was wrong can be traced to bad grounds. When you got sparks when the license plate bracket hit the bed, it was because the lights didn't have a ground path until the bracket hit the bed, not because the bed was hot wired. When you hooked a ground to the socket and the light got too bright, it was because the other light sockets that you hadn't grounded were getting their ground through the filaments of their lamps to the brake light filament on the light you had grounded. If you had grounded all the sockets, that wouldn't have happened.

Sorry guys. Wasn't trying to cause any hard feelings. You are absolutely right, I was frustrated and maybe I was kind of taking my frustration out here. I truly apologize to everyone. I don't know what I would do if I didn't have this place to come to for the resources available here.

With that said, when I got in from work today I made up a ground wire and ran it from the frame rail to the bed. I made sure I cleaned each mounting location down to shiny, clean metal before I bolted it on. Hooray, all lights are working perfectly. Thought I had done that before but apparently I didn't do a good job of getting the surfaces cleaned up.

Thanks again and I hope everyone will accept my apology. Tonight I will have humble pie. :o

no apologys needed here!! if someone thinks they do, then their skin is too thin... :p

if you want us to forgive and forget, post some pix of your work!!