Troubleshooting Trailer Taillights Blowing After Connected to 2009 Toyota Rav4

Question:

I hooked this connector up to my 2009 RAV4 deviating the instructions by, rather than grounding the unit to a panel in the rear, I chose to run a second wire with the power wire to the battery... creating a direct ground. Hooked the connector to the trailer used trailer that is new to me but I saw electrical tape - not sure of integrity of trailer wiring and engaged right turn signal flashing half dozen times or so, then left the same number of times, but it seems when the vehicle signal lever was returned to the nil position the lights blew. Never had functional running lights. After all lights went out, I used a test probe - connected the alligator to ground and checked all three outputs on my vehicle and all seem to work - left and right flash, and running says constant when supposed to. Is it possible running ground right to the battery is causing an over-draw condition on the light filaments? i.e. does grounding to rear of vehicle allow enough additional resistance to keep lights from burnout? Or is it likely the trailer wiring is just screwed up?

asked by: Paul P

Expert Reply:

The problem you described should have nothing to do with the way you ran the ground wire. Having a better ground would not cause your trailer lights to blow.

I strongly suspect the integrity of the wiring of your trailer. I would bet there is a short on the trailer wiring that needs to be addressed. I would inspect the wiring looking for any obvious signs of a short and fix as necessary.

I attached a couple wiring FAQ's that you might find helpful as well.

expert reply by: Jameson C