"Tail light" is kind of a generic term. Can you be a bit more specific about which light is failing? Running light (sometimes called parking light)? Brake light? Turn signal? Backup light?
If you have a short to ground, that means it blows a fuse, probably in the tow vehicle (since that is where the power to the lights comes from), right? And disconnecting that brown wire behind the refrig stops it from blowing?
The TM Owner's Manual has a diagram of how the wires in the roof are routed from the lift arm to the individual rear (outside) light fixtures. If you don't have your manual, try here;
https://www.trailmanorowners.com/for...ad.php?t=13839
The page you want is toward the back, though the specific page number is different in different versions of the manual. Maybe find the page and print it out.
It also shows the locations where connections and junctions are made. Most of the junctions and connections, including grounds, are located very near one of the fixtures, so most access is gained simply by popping the lens off the various light fixtures along the path (especially the failing one), and unscrewing the fixture from the surface of the TM. That lets you actually see the wires and the connections, making it possible to see an abraded or cut spot that is touching ground.
It is possible, of course, that the fault is somewhere along the wire that runs along the driver's side edge of the roof. These are harder to access since I believe you actually have to remove trim to get at them. But they are less likely to develop a short since they are uninterrupted (no connections) and physically protected from abrasion, motion, and sharp edges.
I would start by removing the fixture that contains the faulty light, and examining the wires that are in it and behind it. Let us know what you find.
Bill
Tail lights wiring access
Linear Mode
