What is Easiest Way Circuit Tester to Tap Into OEM Wiring Looking for Stoplight Circuit

Question:

The tekonsha 22117. The red wire on the brake controller harness needs to be splice to the cold side of the brake switch...i am not one to splice into oem wiring. Can i run a red wire to the tekonsha rear kit brake light wiring and splice it there. If so which wire/side to do this. I installed everything but the red wire and while driving into town a brake warning came on...am i causing this but not hooking up the red wire as yet. Will it do any harm or cause the truck not to start?

asked by: Fran

Expert Reply:

Tapping into OEM wiring is a little daunting Fran so I am right there with you. You could use a brake light circuit at the rear of the vehicle if you wanted but again it would come down to testing the wires with a circuit tester till you find the circuit that has 12 volts only when brakes are applied. The easiest type of circuit tester to use is one with a hook and probe like the part # PTW2993 which makes tapping into the circuit pretty simple and easily does so without damaging anything. This would be the best way we can help.

expert reply by: Jameson C