What Amperage Draw Does Brake Controller Look for on Trailer Wiring to Sense Connection

Updated 05/15/2019 | Published 05/14/2019

Question:

Hi, I understand that brake controllers check for a signal draw produced by the brake magnets to “recognize” a trailer is hooked up. My question is, what is the exact signal they look for? I’m making a vehicle/trailer test box. One of the functions into hook a vehicle into it and test the vehicle wiring at the plug. I have indicator lights for each of the functions except the trailer brake signal. I installed a small voltmeter in this spot. My test light shows a faint pulsing from the brake controller. But the integrated brake controller in my test vehicle doesn’t recognize a trailer to be hooked up, therefore it won’t actually power the circuit. Should I wire a resistor in line to duplicate the brake magnet resistance, telling the truck there’s a trailer? If so, what kind of resistance or rather how much?

asked by: Wade

Expert Reply:

Easiest way to fool a brake controller into thinking a trailer is connected is going to be by installing a brake magnet on the circuit as that's the "draw" it's looking for. For that you could use the part # AKBRKR-M12 and you'd be set. The minimum ohm resistance you'd want is 7.5-8.2 ohms which is the normal resistance found on a trailer with the smallest brake magnets offered. If you went the diode route that would be the size you'd need.

I attached a link to a help article that has more info on brake magnet draws as well.

expert reply by: Jameson C