Troubleshooting No Truck Brake Lights When Manual Override Used on Dexter Predator Brake Controller

Updated 11/25/2013 | Published 11/23/2013

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Question:

I have installed the Predator #58-8 in my 2008 GMC Sierra. The installation manual states that the tow vehicle and trailer lights should illuminate when the manual slide is activated. This does not happen. Am I missing something?

asked by: Chris

Expert Reply:

According to the Dexter Predator # 58-8 Brake Controller installation instructions, if your truck lights are not illuminating properly with the manual override is activated, then you will need to check the red stoplight wiring connection. The brake controller red wire should be connected to the non-powered stop lamp switch wire on your 2008 GMC Sierra.

On your specific truck there should be a wiring bundle that is below the steering column, and is to the left of the brake pedal. This is shown in the Helpful Article that I have linked for your reference.

The red wire from the brake controller should also have a 20-amp fuse installed in-line with the non-powered side of the truck stop light switch. This should also already be installed on your truck. You might also check the condition of this fuse and make sure that it is proper working order.

I recommend using a circuit tester like part # PTW2993 and checking the red wire on the input and output side of the brake controller. This wire should have signal when the manual override is activated (both input and output). If it does not, then there may be an internal problem with the brake controller. To be sure you will want to check the connections that lead to the brake controller as well.

I have included a helpful article that demonstrates installing a brake controller on your vehicle and troubleshooting the installation of a brake controller for your reference.

expert reply by: Rachael H