Just bought a 2000 f350 as a second work truck and need to tow my new dump trailer. Installed new break controller and 7 pin adapter on back of the truck (old ones were gross and corroded). Now All the lights work but breaks won't engage. Breaks didn't work with old controller and 7 pin. I know it's not anything to do with trailer, works just fine with my other truck. Thoughts???

 

check fuses both under the hood and in the cab.

Since you have ruled out the trailer as working you will have to start at the fuse block and follow the wires probably.

 

and double check the Ground connections.. both truck and trailer...


do NOT rely on a ground coming from/thru the hitch.

 

Seven pin on truck

 

Does brake controller light up? Does it show any activation? If so then it is downstream from that. If it doesn't work then you need to check power.

 

sorry wrong thread

 

I don't know about the older trucks, but I found 4 frame grounds on my 2018 F-150. If something electrical doesn't work, most of the time it is a bad ground.