I bought a trailer a couple years ago, rewired it. It had a 4 pin, put a 4 pin on it when I put a new harness on it.

Here is the issue, it has electric brakes. To use the brakes, I need to convert both my car to 7 pin and the trailer. I did test them and they do work. Is there a way I can use the electric brakes without changing out the harness?

The trailer has a battery on it, so I figured I could use the Brake signal to trip a relay that connects the battery to the brakes and then releases when I let go of the brakes. I get this is how a brake away system basically works but still needs a 7 pin.

Have the brake light signal switch a relay that connects the battery and brakes

>>2922452 (OP)
you obviously dont have a clue how electric trailer brakes work so you should probably read up on that and figure out which controller you should to install

>>2922452 (OP)
>I figured I could use the Brake signal to trip a relay that connects the battery to the brakes and then releases when I let go of the brakes
this will make your brakes lock up instantly and you will skid out of control.
just do it right with a brake controller