Troubleshooting No Running Lights On A Towed Vehicle With The Roadmaster Invisibrake

Question:

Moved a Invisi-Brake system from our Chevy Spark to our 2021 Ford Bronco. Installed a Curt 58996 Towed Vehicle RV Harness and all worked perfect. Then installed Invisi-Brake and our running lights do not work Do I need to install diodes in the lighting wire harness? If so what size diodes and which wires require them? Ive removed the power fuse yet still have this problem.

asked by: Dave W

Helpful Expert Reply:

If you installed the Curt 58996 and everything worked until you installed the Roadmaster InvisiBrake Supplemental Braking System # RM-8700 then you most likely have an issue with the wiring. You can trace the running light wire from the RV end connector of the wire harness with a tester # PTW2993 and work your way towards the tail lights on the Bronco to see where the signal is being lost and fix the connection.

The controller for the Invisibrake # RM-8700 would splice into the Curt wire harness but should not affect the signal from passing through to the tail lights as long as you spliced it in correctly. The diode info you're seeing in the Invisibrake manual is there because they intend for you to use their wire harnesses as well. The Curt harness you used is a bit different and wouldn't need diodes.

Check your wiring to see where the signal is being lost and your connections between the Invisibrake and Curt wire harness and let me know what you find and we can troubleshoot further.

expert reply by: Kevin C