https://www.hwhcorp.com/ml13514.pdfThe 40 amp fuse supplies the silver control box IF you have the 2001 model still. It goes to the control box(wire 6100). AT the control box is a 1/4 inch stud that a large gauge (10 gauge) ground wire is secured to that stud. IF that ground wire is not secure or the ground feed from the chassis source is weak/corroded, THAT will cause that type heat and failure on the 40 amp fuse. Pages 27 thru 29. Doug
PS, The white ground to that control box on that stud comes direct from the Ground wires AT the HWH pump mount bolts that hold the pump to the steel chassis mount plate. Verify the ground bolts are TIGHT on the 2 bolts on the pump mount.
