How to Identify a Ground Wire to Replace Lights

Question:

I recently purchased a 1982 Skamper Popup and am replacing the lights with LED since the existing marker lights were all broken. Im trying to figure out how I should wire this since these are located on the roof which doesnt have a logical place to ground to. The wiring diagram that came with the popup doesnt match the colors Im seeing on the trailer, and the wiring harness appears to have been replaced with a 4 pole. I am assuming that white is negative and blue is positive. Can I connect the ground to the negative wire?

asked by: Diane

Expert Reply:

The best way to find out if you can use that as a ground is to check the white wire with a Digital Multimeter like item # PT89ZR. Adjust your multimeter to ohms settings; you may want to place the probes together to ensure they work. Then attach the black probe to the exposed pin of the plug and the red probe on your grounding wire. For adequate grounding, your multimeter should read about 0.3 ohms. I recommend doing this closer to the wiring on a light you are wanting to replace as well just to make sure they used the same color wiring throughout. Touch the white wire with one of your probes then find a good grounding point with the other to verify that white wire is still being used as a ground.

You could also follow the white wire from the connector and locate the point where it attaches to the trailer frame, which is usually on the trailer tongue, to be sure it's being used as a ground.

expert reply by: Jerred H