Originally Posted by FE28Z
Thank you for the information. Yes, I have the same style of light and agree that it is not a robust design.
If I have to run a new ground wire, the shortest path to ground that I see, would be from the middle clearance light to the vent in the upper bunk area. This is about 18" and I've confirmed there is a good round wire there.
So the approach would be to drill 3/8" hole through the base of the clearance light (under the amber lens) then snake a wire through to the vent area. This would work unless there is no open area (air gap) between the ceiling of the cab and the roof of the RV. Does anyone happen to know if there is a 'gap' between these that I could run the wire through?
Safe money then, is on corrosion right at the fixture. The bulb socket. This is where you probably need to spend some time looking.
The foam gaskets compress, then eventually melt (you can see it in my earlier photo), and the fixture design funnels water right in. It's not really set up to cause a roof leak, but water does get held nicely in the little cup-like fixtures
but to answer your question.
there is a gap, under the radius nose cone surface anyway. the wires from the fixtures just hang more or less loose in there. I was able to pull them out to splice in the new fixtures, and then feed it back in.
It was tricky though, since there was not enough slack to really pull some of them out nicely. the wires are anchored inside that void somehow.
But as for fishing a wire..... as you are getting back to the flat roof area, there is a metal frame structure, and insulation in the void.
As I tried to get at earlier, I think a better approach would be to figure out how to remove the ceiling in the overcab bunk area. I haven't done it, but based on my poking around up there I feel like it would likely be fairly easy to pull loose.... find the trim covering a seam or at the perimeter to get an edge to work from.
The outside skin forming the radius is thin FRP, on the order of 1/8in thick. You can deflect easily when pushing on it....
as you can the ceiling panel, which seems to be a thin sheet material of some kind too...
so Based on what I saw from the outside with my light fixtures removed, I feel like there's a more or less open void, and you could see all the wiring quite easily.
From there, if you really do have to run new wire you could just follow the path of the original harness.... but I would doubt you would need that as I'm betting it's either corrosion or simply a poor connection someplace.
If you do go this route, I would appreciate seeing some pictures!
oh, another thought.... unlikely I'm guessing, but let's say that it is bad wiring someplace other than at the fixtures.... might be worth checking at the other end of the harness first, if you can figure out where that is.... just to verify that the problem isn't down at the switch or someplace else other than the roof.
I'll bet you'll find the harness diving down to the frame and underside, in the wall behind the driver's seat. According to the crude diagram I was able to get from Thor, it looks like its a brown wire and a white wire going to these lights.
And one last thought for now.... I was just at Camping world over lunch. They had some clearance lights on shelf, that looked like promising replacements.
LED Cab Light; Amber; 15 Diode - Optronics International Llc CBL22AS - RV Clearance Lights & Lenses - Camping World
You'd probably be left with some screw holes to fill, and probably some ghosting in the finish where the lights aren't exactly the same size/shape..... but I'll tell you, if I ever have to dig back in up there I'll be looking for something like these almost certainly.