How to Prevent Backfeed to Brake Controller When Testing Breakaway System

Question:

Your posted reply to backfeed protection for the tow vehicles electrical system indicated the chances of damage from activating the emergency breakaway system are slim to none. However, the Tekonsha Primus IQ brake controller instructions say to disconnect the 7 wire connector or the brake controller will be destroyed when the emergency breakaway brake is employed. So could there be damage or not? Since I could see myself testing the breakaway system and forgetting to pull the 7 wire connector, Id hate to blow up a controller. So is it really a slim to no chance...or is a diode needed to protect myself against forgetfulness...and if so...between what wires do I install the diode? Id think inline of the brake controller wiring harness in the cabin would be best?

asked by: Duane

Expert Reply:

Most current brake controllers, including your Tekonsha Primus IQ # TK90160, actually have built-in protection that prevents potentially damaging backfeed when pulling a breakaway pin with the trailer still connected. With that being said, it's absolutely still recommended to first disconnect the trailer when testing the breakaway system just to be absolutely sure (keep in mind that in the event of an actual breakaway situation on the road, the trailer connector would become disconnected so backfeed wouldn't be a concern).

If you are worried about remembering to do this when pulling the breakaway pin for testing, then adding a diode certainly wouldn't hurt anything and would give you complete peace-of-mind. You would add the diode # RM-690 in-line with the blue brake output wire on the tow vehicle, anywhere between the brake controller and 7-Way connector (at whatever spot is easiest to access).

expert reply by: Chris R