I have a 97 e-superduty. Hooked up boat trailer up to the rv plug first time and blew fuses in power box. Replaced fuses and still have no brake, turn signals, or hazards on van. (not hooked to boat). All fuses are good in fuse pannel and power distribution box under hood. I have running lights. Where else or what else do I need to check?

 

Could this be a grounding issue? Lights started to work with nothing new being done. Could turn signal switch be going out?