Trailer Brake Lights Go Out When Brakes Are Applied on a Trailer Towed by 2009 Hyundai Sonata

Updated 09/19/2012 | Published 09/16/2012

Question:

Brake lights work once then i have to take out bulbs on trailor. Tested inside trailer lights and when bulb is in i have no power to when i take bulb out i have power. Checked plug at back of car works every time. Replaced ground on trailer and still same.

asked by: Don

Expert Reply:

You will want to look at the grounds and wiring for the lights themselves. This sounds like a ground or short circuit issue. Trailer lights ground through the mounting studs unless there is an obvious ground wire. In either case the grounds need to be attached to clean and corrosion free bare metal surfaces.

When you inspect the wiring, look for any nicks with exposed wire that could be touching the metal trailer frame. This would cause a short. I have included a link to our wiring FAQ that has a section on wiring troubleshooting that might also help.

expert reply by: Michael H