99 Explorer blows heater fuse

[Knife Collector]

Heater stopped blowing, figured out it was the 40 amp maxi fuse in the box under the hood. Replaced it, and a couple minutes later it blew. What do I need to check for to find the cause of it blowing?
Any help is appreciated..

 

[coco944x4s]

Does the fuse blow even with the fan motor off or does it only blow with the fan motor turned on?

 

[Knife Collector]

Only when on. Ran for about 2 minutes.

 

[coco944x4s]

I would definitely be looking at the blower motor being bad. If its popping the fuse, its bound to be pulling too many amps trying to make it work. Does it matter what speed its on? does it only do it in high, or does it do it on any speed?

 

[Knife Collector]

I replaced the fuse again, and didn't turn it on, just the minimal flow it gives, and it never blew,, I didn't have it on high, maybe on 2nd speed.
I thought I heard a knocking or pecking sound right before it blew... then stopped after I noticed the fan quit.
So your prolly right about it being the motor.