Originally Posted by Frankp877
I've done the same thing with my jack and for the life of me I can't find the fuse. Is it inside the camper or out on the tongue? There's a wire look that runs along the tongue then into the camper. Could it be in there?
In my case the jack is wired directly to the battery and has an In-line fuse holder between the battery and the jack. There is a second wire to a different type of fuse on the power to the trailer. There was no negative wire as the jack grounds to the trailer frame. Initially, I thought that the ground might have been poor and added a wire from one of the jack bolts to the battery negative. I figured it could not hurt anything and there would be less voltage drop.
If the jack is wired from the inside of the trailer, your issue could very well be that there is too much of a voltage drop to operate the jack when the battery is on the low side.