Originally Posted by Timex
What causes a fuse to blow?
a fuses job is to protect a circuit from a direct short to ground. it is the weak link in the system. a circuit breaker is very similar also with slightly different operation but in the end provides the same function.
let's make a simple light circuit. power must flow from the positive terminal of the battery through the lightbulb and then to the ground, the ground can be the trailer frame or a wire leading back to the negative battery terminal. a fuses is put in between the positive terminal and the load which in this case is a light bulb. a fuse needs to be placed as close to the battery connection as possible for proper protection. if you did not have a fuse and the positive wire were to touch ground it would arch in turn causing a dead short which can cause damage and possible explode the battery. basicly is is welding metal in a simple answer.
The fuse can blow from a direct short to ground, the fuse being lose in the holder causing heat in turn melting the fuse, the motor being shorted or bad, or a bad connection causing high resistance.