Troubleshooting Tow Bar Lighting that Doesn't work When Running Light Is Turned On

Question:

I have a roadmaster hitch and wiring setup. While travelling, I lost my toad lights and all fuses were still ok. I ended up buying a blue ox 7 to 6 adapter. It was all they had available. When I hooked it up, it worked fine as I only did daylight driving. A month ago, I was pulled over in Texas and was told I needed my tail lights to work. They worked on the motor home and all lights work on the toad except my tail lights. No fuses blown. Checked the toad wiring with volunteer and taillights work at the toad connection. What could the problem be if all fuses are ok and both vehicles are fine when unhooked.

asked by: Brent W

Expert Reply:

Typically when a lighting functions stops working when the headlights or running lights come on, and the circuit is active at the tow vehicle connector the issue is an insufficient ground. What happens is when you turn on the headlights of a vehicle you end up putting quite a bit more amperage on the lighting and charging systems due to the draw of all of the light bulbs. So if there's a weak ground anywhere it's going to show up in this situation.

So what I would recommend is try improving the ground wire connections on the tow vehicle and towed vehicle side of the wiring to see if that helps that circuit work.

expert reply by: Jameson C