Remember----The hitch ball is NOT an adequate ground. Make sure the ground wire in the TRAM is installed in the receptacle for the plug and IS grounded to the frame of the Tram. I doubt the ground on the tow truck is not installed correctly. To verify ground issues is simple. Take a jumper cable and connect one end to the truck frame and one end to the Tram frame. If the issue goes away you have that ground wire problem. The other issue if not a ground is HOW the Tram tow end plug is wired. Odds are it is NOT wired to code and correct. Doug