Heater

[pjmoreland]

Originally Posted by Frogurt

I forgot to say, when I don't have the truck running and it is just on accessory it will work on high forever but as soon as I start the truck it blows the fuse.

The alternator raises the system voltage. Higher voltage results in more current to the blower. Your 10A fuse must be right on the edge of working on 12.5V battery voltage, and the slight increase in current when you've started the engine is enough to push it over the edge at 14.5V.