Good Afternoon from Florida!! I have a two year old Goodman Model GPC1242H41CA package unit that has heat strips, I had a short that eneded up causing me to replace the transformer and the control board. I ended up replacing the thermostat and wires as well and now the AC side works perfect but when it is changed to heat it blows the 3 amp low volt fuse and heat will not work. I replace the fuse and turn it back on to heat and it again blows the fuse....I dont understand why the cool works fine but the heat is blowing the fuse. I have checked the heat strips and nothing is broken or touching anywhere so I am kind of at a loss right now and could use some advice. Thanks!!!!!!
My guess is there is a short in either the W wire or in one of the heating components. If it happens immediately it is probably in the W wire. If it goes for a while it is probably in one of the components and when that component is energized the fuse blows. Try disconnecting the thermostat wires from the unit and jump R to W. If it works your problem is in the thermostat or thermostat wires. If it stil blows the problem is in the unit itself. They do make things called poppers that are basically circuit breakers instead of fuses that fit where automotive fuses go. Saves a lot on fuses when not sure where the problem is.