The customer stated that the rear turn signals worked but not with the tail lights turned on and the stoplights did not work at all. Having been down this road many times I surmised that there was a faulty ground somewhere and started checking the basics like loose connectors and loose ground bolts but I found none. When working with dual element bulbs, if both elements are dimly lit with only one control signal turned on ,you have a faulty ground to that bulb and if the condition is repeated in other bulbs you have a faulty system ground.
I decided to test the ground and could not find a ground at the main harness in the rear. I used a jumper wire to attach a ground temporarily and had someone observe the light to see if it lit up properly so that I could narrow my search. I was told it did so I moved my jumper wire and asked if the bulb had gone back dim again. I was told “no it is still bright”. This isn’t good. I must have moved something to make the ground come back. Time to drop back and look at the big picture. What has been done to this vehicle recently? I looked around and I found a hose clamp slightly out of position and noticed scratch marks along the frame rail and on the gas tank. Someone has recently put a fuel pump in I thought. With this in mind I decided to pull the main harness part way out and inspect it.
As you can see in the pictures the harness was damaged at forward edge of the fuel tank assembly. Apparently the installer was having some problems and forced the tank into place with the harness hooked on the edge of the tank and cut two wires completely in half and damaged several others.
A few splices and heat shrink tubing to repair the damage and all is well. On the wires that only had damage to the insulation, I removed the wire from the plug in connector and slid heat shrink tubing back up the wire to seal the damage. Taking a little extra time to do this, kept me from having a large knot of splice connectors in one place in the harness which could cause further problems for the customer at a later date.
