Trailer Brake Lights Go Out When Stepping on Brakes in a 2007 Buick Terraza

Question:

Vehicle has factory installed trailering package and all lights work normally. When you plug in the trailer harness the trailer brake lights go on but when you step on the brake the brake lights on the trailer go off. All other trailer lights work normally and when you connect the trailer to a different vehicle there is no problem. Thank you.

asked by: David M

Expert Reply:

What I think may be occurring is the power draw on the trailer that has the issue is too great for the electrical system on the 2007 Buick Terraza. When you step on the brakes there is more power going to the lights which does not allow them to illuminate correctly.

If the trailer has a lot of running lights this may be causing the issue. Check the vehicle owners manual to determine how much power the tow package can handle and compare that to how much power the lights on the trailer require.

Another possibility is a ground issue on the trailer, but since it is working on a different vehicle this is less likely. Still, you can check the trailer connectors for dirt and corrosion and make sure the grounds on the trailer connector and at the lights are all connected to clean and corrosion free bare metal surfaces.

You can also check to make sure the wiring harness is installed correctly. The harness we carry for your vehicle, # 118396, plugs in line with the tail light wiring with the green wire going to the passenger side and the yellow going to the driver side. I have included a link to the installation details and a link to a video showing a typical installation for you.

expert reply by: Michael H