Originally Posted by ratovan
I took a circuit tester out and sure enough the battery lead and the right turn signal lead where hot (power going through them).
The 7 way on the trailer doesn't seem to have any way to remove the connectors to inspect the wiring. Do I assume that my only recourse is to cut off the 7 way plug on the trailer and replace it?
Well, the 12 volt + should be hot as that goes to your battery in the RV, but the right lights shouldn't.
You may have a molded plug on the end of your umbilical cord. However, I would still follow the cord back on the trailer frame to where it probably enters a junction box. Your trouble could be at that end of the cord. I would definitely check there before trying to cut the 7 way plug off the cord.
Are you using a circuit tester that just lights up, or perhaps a multi-meter that shows how many DC volts are on the right light? The reason I ask is you could have another problem, that is a lot more complicated and I don't want to get into at the onset. It would entail your frame being hot. Let's stay with the simple stuff first.
Just for grins, did you also check the brake wire (#2 in the pic above) to be sure it's not hot too in the 7-pin connector. It shouldn't be.
Something else to try, is to put the bulb back, then start wiggling the cord and end to see if the light goes out (or turns on if it isn't lit up). That may help you determine where/if the 12 volt hot wire and right light wire are touching each other.
You may want to disconnect the battery first before reinstalling the bulb, so it doesn't blow out when you put it back in. Once you reinstall the bulb then hook the battery back up and start wiggling. LOL
I have to wonder if gravity is the problem. When you have the 7-pin plugged into the tow vehicle, then gravity would pull a possible loose right light wire inside the 7 pin down and away from the 12 volt + terminal. Then if you just let the 7-pin hang after disconnecting, then gravity may actually pull the right light wire over to the 12 volt + terminal. You should be able to test that theory and move the plug into different positions (horizontal and vertical) to see if the right lights go off/on.