Working on a sterling 2008 No brake lights on R side only got 5 volts to rear of truck?
look for chaffed or bare wires somewhere between the back of the cab and the taillights. Does it have a junction box at the back of the frame? If so look in there for corrosion and bad connections. Sounds like you’ve got some green wires somewhere
Last weeks spilled coffee/coke/water jug fluid in the rear cab floor area maybe??
That was all back probed. We seem to have it when you put a heavy load on it. We just put in a new controller in and looks like this was the problem. Thanks for your help.