Heater/Fuse Question

When i first got my bronco, my heater worked every time, no matter if it was high or low, or running all day; I could always count on it. Now it seems as though, every time I try to run my heater, my fuse blows instantly. For a while, I could make it run on low and just barely turn the knob to a perfect position for off. (Almost like have an original Nintendo, you had to have it just right for it to work, and only you could fix yours) I just dont understand why it keeps blowing the fuse, no matter what the speed is. I have an extra blower motor, and thought it was the issue for some reason, but the old one works great. My heater core has been replaced within the 2,000 miles. Could be a resistor? or bad ground?.....Im just open to suggestions at this point.

Not likely a resistor or bad ground; those would cause too LITTLE current to flow, and the fuse blows when too MUCH flows. If your spare motor works, test resistance thru both motors & compare.

I agree. Also could be rust in the fusebox. Rusty terminals cause heat and melts the solder in the fuse.

I recently had the rusty terminal/melted fuse experience with the heater fuse.
SHX