When I got my GTC, only one taillight sort of worked. None of the clearance lights worked and neither did the dome light. I also had a slow battery drain. A friend and I spent a lot of time trying to figure out what was wrong with the exterior lights. We started at the taillights. While Hall generally did a very good job in routing the wiring, they crammed a lot of connections behind the left taillight which happens to be under the shower. Someone in the past had added trailer wiring by doing splices into the factory harness. A lot of these were bare wires at this point so we started by cleaning that up. Still had no power to the left taillight or to the clearance lights at the rear. Grounds weren't the problem.
We then headed to the front of the vehicle to start from that end. You need to pull the instrument cluster loose to gain access to the harness. There is a square connector where you can disconnect the harness to the rear. Power at that connector was good for all functions. The harness comes out at the top of the dash and then goes up the left windshield pillar and up over the cab. Next we pulled the panel covering the A/C unit over the cab to gain access. Once you pull that off you can see where the factory Dodge harness is tied into the Hall wiring. Everything looked good there but I noticed that the wiring harness was resting on the sharp steel edge above the door where they cut the van cab roof out. I grabbed the harness to move it away from the sharp edge and all of a sudden lights started to come on.
This led me to think that there must be a short in this area. In fact that wasn't the case. Instead it turned out that the wiring was shorted out where the harness goes into the top of the windshield pillar to the over cab area. Normally there is plenty of room there for the harness but Hall ran one of their harnesses through the same hole. I cut the harness off near where it was tied into the Hall harness and taped a long wire on the end so that I could use that to fish the new harness back in. If your rig has the factory coach air system there is not much room to work.
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File comment: Arrow points to where harness tucks in behind windshield gasket. At corner above vent window is there harness goes through hole to up over the roof.
light_harness3.jpg [ 85.31 KiB | Viewed 8892 times ]
light_harness3.jpg [ 85.31 KiB | Viewed 8892 times ]
I got a new harness from the junkyard. It looks like any 1972-77 Dodge van is a good source. I just cut it off long enough to have plenty of length to reconnect everything. Now fishing the harness back into place is a real pain. I had to cut the dome light connector off because there was no way I could get it through the hole with the Hall harness in there. I taped the new harness to my fishing wire and it was a lot of work to get it through there as I was working on my own this time. I probably could have removed the terminals from the dash connector end and gone the other way but didn't think to try that until I was already going the other way. Once I got it in place I had to pull the harness down and add more tape to it where it went through the pillar hole to protect it from rubbing through again.
Attached are pictures showing a replacement harness and also where the wires were broken in the original.
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light_harness1.jpg [ 143.37 KiB | Viewed 8892 times ] |