so the problem starts with...
installed a LED light bar on back of truck. I used the 4 pin plug that was included into the 4 pin plug under the 7 pin on the receiver. intermittent connection, in the process of jiggling it one wire comes out of the back of the factory 4 pin connection. I cut it off completely and stripped wire back as far as the wiring pigtail would allow and still have room for connectors, the wire was black inside the insulation on 2 of the 4 wires. Got it wired up, all worked fine.

fast forward a couple weeks. installed some new LED lights on travel trailer and drove about 450 miles, mostly at night, all worked great. heading back and turn on lights, no trailer running lights (all other functions work fine.) I check, and the 20 amp fuse listed as trailer running lights is blown. replace it, blows again. uh oh.

Start looking over trailer, cannot find any shorts etc. look at LED bar, again, so sign of shorts.

Replace fuse one more time - does not blow - but have very low voltage to trailer lights. now I start thinking maybe it is a ground. Am about 60 miles from home, decide to limp it on home with barely lit running lights, but other functions fine. go 2 miles, no more running lights. fuse is NOT blown. check voltage at trailer plug - 0.

Replace fuse, just in case, nothing. check all other fuses, nothing blown. replace relay, nothing. I am getting no voltage at trailer plug.

Ideas?

 

Any ideas out there? A guy who works on semi trailers said there should be a voltage regulator that may have gone bad. I have not found any reference to a voltage regulator for the trailer wiring anywhere else.

 

Check your ground wire! If the trailer doesn't have a good ground, that can happen. I spiced into mine(white wire) in the pigtail(near connections at trailer) and then put an eyelet on it and screwed it to the frame. My problem was solved. Then check the ground for your truck. Find the connection under the rear of the X(where plug wires come from) and check power there. You may have also shorted out the plug itself..

Don't know of a voltage regulator for the wiring...