Tips for Finding Brake Light Circuit on a Vehicle Where Its Not Present Near Brake Pedal

Question:

I am trying to locate the brake light switch on a 2006 International 4300 with air brakes to connect a trailer brake control. I have found the inline switches under the dash near the brake pedal, however I cannot find one with power out when the pedal is depressed. Are they possibly just closing a circuit so there is no actual power to ground at the switch? Thanks for any help.

asked by: Karl C

Expert Reply:

Typically the brake switch circuit is found near the brake pedal, but for larger vehicles like yours it may not possible to find it there. What we normally recommend then is to find the wiring that runs to a third brake light and use it as the stop light circuit for the controller. Sometimes at the fuse box you can find the circuit for the third brake light as well as the CHMSL circuit.

You would need to be sure and not use a circuit that also carries a turn signal circuit.

For testing the circuits you may need a part # PTW2993 as well.

expert reply by: Jameson C