How do the tail lights ground?

[jstone4646]

I have nothing on the rear lights wise. I found the plug along the frame and plugged it in but still nothing. The bed was removed by the previous owner along with just about every ground wire on the whole truck so my guess is a ground wire is missing. bulbs are brand new.

[grumpin]

This is from my 1986 manual.

[FuzzFace2]

This is from my 1986 manual.

You did not say if style side or flare side so will post what I have seen on my 81's, 1 of each.

I would first start at the fuses. I would pull each one and test with a ohm meter.

If you check in place note not all fuses have power to them all the time. Some only have power when that system is turned on and the truck may need to be running or the key turned to run.

Once you know all the fuses are good and of the right amps you can find the 1 for running lights and with the truck running, lights on check that fuse if it has power in & out of it.

Now outside the truck on the inside frame rail where the floor & firewall meet the rear wiring harness plugs into the trucks main harness.

I would pull this apart to make sure it is in good shape then test for power to the rear lights. Remember the switch has to be pulled out (on) to get power at that plug.

You will have 1 wire that the power will be about 5-7 volts or if using a test light will blink. This is normal as it is the fuel gauge sender wire.

If you have a helper or jump out the brake light switch, Think 2 other wires will have power to them. This would be the left & right turn/brake light power wire.

You should also have another wire that would have power when the reverse lights are on.

So you should have wires in the plug for:

right turn/brake light

left turn/brake light

running lights

fuel sending unit(s) (if duel tanks you may have another wire that would blink when the other tank is switched to)

wire to the switching valve depending on year and motor

reverse light

and may have a ground

When at the back IIRC both of my 81 trucks had another harness for the rear lights that plugged into the frame rail harness.

I would check for power here before plugging in the light harness.

Should have:

right turn/brake light

left turn/brake light

running lights

and may have a ground

Now my flare side was a mess at this point so cant help much but from what I have found (could be wrong also) each light was grounded to the body. I can no longer get factory lights so I will do what is need when the time comes.

On the style side the lights had a ground wire that was screwed to the body behind the light. Some have said they don't have this and the lights ground thru the wiring harness.

Either way if you don't have power back there a ground will not make a difference.

Dave ----

[85lebaront2]

All of the rear end of the truck actually grounds inside the cab at G701 which is under the dash RH side near radio. It goes through two connectors to get there (this is from the 1986 EVTM which is on this site) C126 is the one at the LH rear of the frame and is single wire brown connector, the larger 4 pin is C1002 and provides the power to the lights C127 is underhood on the driver's side of the firewall. I swore years ago that the engineers who did the wiring on these trucks were on some serious hallucinogens when they designed it. If you can't find the mating piece for C126, you can try grounding that wire to the frame.

Good luck with it!