Troubleshooting Prodigy P3 Brake Controller Install Where Truck Fuse Keeps Blowing

Question:

In short, not a pun. I have been asking the experts numerous questions, mostly speaking with Jamison C. The first P3 I have stopped powering up only to find that the 30A brake fuse was blown. After several attempt to solve the issue, and nearly burning a hole in my hand, I called Horizon and spoke to a guy there name Kirk. I described the fuses blowing, the p3 getting super hot. He said there was definitely an internal issue and shipped me a new one. I plugged it into the truck today 7/10. The original plug in harness was still connected to the truck. I plugged the unit into the harness and the screen stayed black. The fuse had blown instantly. Now Im befuddled. I had told Kirk that I hooked up an older Reese controller and it did not blow the fuse and operated correctly without the trailer connected. All this is happening minus the trailer. I had an instance where the 7 way might have gotten wet while using the 7 to 4 adapter that I dont really need I figured out. I wondered if this might be the issue. I sprayed all the connections with contact cleaner. QUESTION: Should I try the other harness from the Reese? What can go bad with the harness as it stands? Perhaps I should call Horizon again? Or have it hard wired bypassing the firewall panel? Any ideas? Thanks

asked by: Paul

Expert Reply:

Did the older Reese brake controller use the same harness that your P3 used? Or did it use a separate harness from the P3? If that's the case I'd say somehow there's a short there causing problems. The fuse blowing indicates that the power wire for the controller is shorting to ground so most likely there's somehow a short between the black and white wires of the brake controller wiring which at this point seems to point towards the harness.

expert reply by: Jameson C