If it looks like a small rectangular cube with 2 terminals, its more than likely a circuit breaker to protect the trailer/travel vehicle. If wires were cut and not spliced together than yes this would stop power from going both places. The wire like this on our 63 was Orange, but you'd need to see with your battery in the trailer connected, (but travel vehicle disconnected) which wire under there is constant 12v
, that should be the one. Also depending on your travel vehicle your 12v
circuit to your plug on your bumper might not have a fuse, on our 2003 chevy it had red fuse blank in that slot that once changed out provided the 12v
to the trailer.