I have probably run my jacks up/down 20-25 times this season, for the second time, today, I blew my LR 20 amp fuse, everything seems ok voltage to all 4 corners is the same, nothing loose or frayed....
I have some 2005 model 4500s that have 30 Amp fuses, one for the left side and one for the right side. Mine were blowing right side fuse because I had two bent jacks. One had a 5/16 inch bow. Straightened them and no longer have a fuse issue.
Check your users manual, as 20 Amp fuses might be a bit small.