Troubleshooting Trailer Wiring that Doesn't Work,Trailer is Fine and 4-Way Pins Have Voltage

Question:

When I plug my camper into the 7way round RV plug all lights/signals work. A friend was going to use my camper and only has 4 way flat on his vehicle. In the past I used a 4 way to 7way conversion and lights worked fine. Tonight they would not work. When I used a light tester on the 7way car side with it plugged into 4way flat the tester showed lights working but when I plug camper in they do not. Any idea why, clearly I get power to the 7way but its not transferring through to camper.

asked by: Sean Q

Expert Reply:

Since there is voltage on all of the pins of the 7-way and the 4-way when the adapter is used and the trailer seems to work fine with your vehicle the problem has to be the ground circuit of your friend's 4-way on his vehicle. It must be corroded or dirty and that is why the trailer light circuits aren't functioning properly.

expert reply by: Jameson C