What Does Brake Controller Look for To Sense a Trailer Connection

Question:

I am working on building a vehicle and trailer testing box. I would like to have a circuit built in to it that makes a truck think there is a trailer attached and will send out voltage on the wire for the electric brakes. This is so I can have a volt meter measuring how much voltage the truck is sending and make sure it is linear. Would hooking up two 6ohm 50w load resistors in parallel to the blue brake and white ground wires off of a pigtail plugged in to the 7way plug on the truck make it think there is a trailer connected and therefor send voltage, or does the truck sense a trailer hook up a different way? Im asking because I hooked it up to a truck with an aftermarket controller and it didnt light up to say there was a trailer there unsure of the aftermarket TBC make or model and I dont have another truck to test on currently, so I cant conclude if the truck, or my setup is at fault. It will be used mainly on newer 10 years and newer Ford, but would like it to work on all vehicles.

asked by: Brad

Helpful Expert Reply:

For a brake controller to sense a trailer connection it needs to sense a small amperage draw on the circuit as that's what happens when the circuit is connected to brake magnets. Resistors like what you mentioned should work well. Or you could wire in a brake magnet like the part # AKBRKR-M7 on the circuit and that would do the trick too.

expert reply by: Jameson C