How to Find COLD Side of Brake Light Switch for Hardwiring Brake Controller
Question:
How do i get a hot wire off of brake light switch
asked by: Dave
Expert Reply:
When you are hardwiring a trailer brake controller like the Prodigy P2 # 90885 the red wire connection that provides the triggering signal to the controller should be made to the wire on the COLD SIDE of the brake light switch circuit. This is the wire that carries 12V power ONLY when you press the brake pedal and at no other time. Please refer to the linked photo and article for more details.
If you were to connect the Prodigy to the HOT side wire then the controller would constantly generate brake output to the trailer and you would not get too far.
Applying a circuit tester like # PTW2992 is the best method for finding the correct wire at the brake light switch.
Dan S.
4/1/2020
2016 Thor ACE motorhome built on F53 chassis.Every one Ive talked to and everything Ive read online insists that I have a plug and play connector in the dashboard. However, after removing the dash and searching through it, theres nothing even resembling one. There are several unconnected wires, but they have labels for PTO and blower motors. Not sure what you mean by Brake Light Switch, do you mean the switch thats activated by the pedal? Those are the wires Im referring to. There are 4: one is constant 12v, one is constant ground, the other two are the ones mentioned above. Where else on the vehicle could I access the cold side?
Dan S.
3/30/2020
Tekonsha says not to connect to a wire that goes to ground when the brake pedal is not depressed. I have 2 wires in my brake position switch that get 12v when brake pedal is pushed, but they both go to ground when it is released.Any thoughts?
Products Referenced in This Question
Product Page this Question was Asked From
Tekonsha Prodigy P2 Trailer Brake Controller - 1 to 4 Axles - Proportional
- Trailer Brake Controller
- Proportional Controller
- Electric
- Electric over Hydraulic
- Automatic Leveling
- Under-Dash Box
- Dash Mount
- Up to 4 Axles
- LED Display
- Up to 360 Degrees
- Tekonsha
more information >
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Claude W.
5/1/2024
I am wiring this brake controller to a 2019 freightliner Cascadia. I plan on also using your trailer connector adapter that connects the two different style plugs. Can I run the brake output switch wire to the module and then run the blue back to the other end of the brake switch output? Its going to the same place and I do not see how it would interfere with the tractor brake lights. Thanks