Troubleshooting Lights on Trailer Towed by Motorhome  

Question:

Expert Reply:

If the trailer towed by your motorhome has lights on one side that do not work the issue is likely to be on the trailer. You could have bad bulbs, loose wiring or corroded connector contacts on the trailer plug.

Check all contacts on the trailer plug, looking for even slight greenish or whitish discoloration. It is possible the issue is nothing more than slight corrosion that you can clean off with an aerosol electrical contact cleaner like Caig De-Oxit. Check all bulbs and bulb sockets for the affect lights, for the same corrosion, or blown bulbs.

You can also test the trailer lights, independent of the motorhome wiring, by directly connecting a charged battery to the pins on the trailer connector. A set of jumper cables and two lengths of wire allow quick and easy connection to any well-charged battery. Connect battery ground to the ground pin on the trailer plug; then connect the positive wire to each circuit on the trailer plug, one at a time, to see if they function.

If not, check the main ground wire for the trailer's wiring harness. This needs to make solid contact to a clean bare metal surface. If the lights DO work with direct battery power then you know the issue is likely to be on the motorhome side. Repeat the same checks for a bad ground, loose wiring and corrosion.

If you have a circuit tester like # PTW2992 you can test the motorhome connector to ensure the lighting signals are present. If not present check your fuses and wiring harness installation.

expert reply by: Adam R

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