There is some type of electrical device located on the drivers side engine compartment, mounted to the inside fender. One wire comes from the fuse box location. Any idea if this is a stock item? If so, what is it for? 1994 F350, 4x4 5.8L

 

That is a circuit breaker. I would bet it is for the trailer brakes

 

That would make sense, the previous owner used it for towing. Thank you!