Troubleshooting Weak Ground on 2004 Silverado and Trailer Wiring

Updated 04/23/2018 | Published 04/19/2018

Question:

Hi I have a 2004 silverado that i do tow with all the time. I’m experiencing a problem with my trailer lights for the first time. When I turn my headlights on in the truck with the trailer connected, my trailer tail lights just stay brightly lit like I’m applying the brakes but I’m not. When I shut my trucks headlights off all lights on the trailer proceed to work properly with no problems whatsoever. Doesn’t matter if the trucks engine is off or on either just when the headlight switch is turned on and off. What could make my trailer lights stay in the brake applied position when my headlights are on but everything work fine when my headlights are off. I’m stumped

asked by: Christian K

Expert Reply:

No worries. What you describe sounds like the classic case of a bad ground. Because vehicle headlights use a fair bit of power and remain on continuously (rather than blink) they often are the lighting function that causes a weak ground connection to reveal itself.

Find the main ground wire from the truck's trailer connector and find where it attaches to the truck metalwork. You may need only sand off this grounding point so that you can re-attach the ground wire to clean bare metal. Often that is all that is needed. The new clean ground can be protected by applying dielectric grease like # 11755 which will block water and dirt that could again lead to a connection issue. You can do the same thing on the trailer main ground wire too.

expert reply by: Adam R