Check your 7 pin connector on the MH, make sure it has a power line running to it. I have a Jeep and installed the jeep wiring harness, it worked when tested on another vehicle, but did not work when connected to my MH. I have towed other vehicles with the MH but always used a converter 4 to 7 adaptor, which always worked fine. Anyway the problem turned out to be that the 7 pin connector on the MH did not have power, which I'm told is common with MH's, my Jeep is a 2012 Wrangler which requires power. Added the line it all works fine now.