On a typical Power Distribution Panel you will find the REVERSE POLARITY fuses located on the 12VDC side of the panel usually off to them self. These will be be two high amperage ATC type fuse. You may also have a 3rd IN-LINE fuse blow which may be installed real close to the battery terminals. Some of the newer trailers use a 12VDC AUTO-RESET Breaker here.
The REVERSE POLARITY fuses are located almost in the center of this google search photo of a typical power distribution panel... (Two 40AMP ATC fuses shown here)
Make sure the battery is back to the correct connections before changing fuses otherwise it will just blow them again. I always look at the battery case for the word 'NEG' or the symbol '-' and make sure this is the battery terminal going to the trailer frame ground. If your trailer is using RED and BLACK battery cables this will be the BLACK CABLE... If you are using BLACK and WHITE cables then this will be the WHITE CABLE. Best thing is to hand trace them out regardless of the wire color...
Roy Ken
