How to Get Brake Signal for Brake Controller on a 1985 Mack Ultraliner

Question:

Dear eT, I am trying to install a Tekonsha Trailer Brake Controller into a 1985 Mack Ultraliner Diesel Road Tractor I know - a weird one. The tractor has combined Turn Signal Brake lights, so its a two wire circuit. I need to provide a signal to the controller when the brake pedal is pressed, but Im having trouble getting to the sensor on my tractor air brake system to get that signal. Im wondering if there is a relay or converter available that will only send the signal when both tail lights the brakes are on? I cant use just one of the brake lamps since these also the turn signal. Can you help? Thanks Joe

asked by: Joe M

Expert Reply:

Hey Joe, thanks for reaching out!

It sounds like you're needing the 3rd Brake Light Logic Module # PP20-702 which connects to both turn signals and only sends a signal on the 3rd wire when both turn signals are lit up. We usually recommend using this for the 3rd brake light on truck toppers but it will function the same for a brake controller.

The only thing that you might consider using instead is the Roadmaster Universal Stop Light Switch Kit # RM-751000 which installs down at the brake pedal and essentially "senses" when the brake pedal is pressed. This has an advantage over the Logic Module because the module will send the signal whenever your hazards are used while this will only send that signal when the brake pedal is pressed - it is a bit more pricey though so there is that factor.

Attached are review videos of each for you to check out!

expert reply by: Jon G