I had a recent failure with the heater/defroster on my 02.
Truck had been warmed up several hours earlier. Outside temp -10 deg F.
I drove a few miles with heater set to vent/floor. Windows started to frost, so I switched to defrost. A minute or two later the frosting was worse. Turned fan to high, and realized it was still on vent, (not defrost), and it failed to full heat, and both LED's on outside air and recirc pushbuttons were on. :think:
Kept driving for 30 miles to destination. Truck idles for about 15 minutes, with same failure. In the fuse block left of instrument panel, I found Fuse HVAC 1.
Pulled this fuse, Hvac pushbutton lights went out, fuse was NOT blown, re-installed fuse, and the heater/defroster started to work as expected. Has been working since.
When I pulled the fuse, the truck was still running, so I'm not sure if I would have just turned the truck OFF, if that would have fixed this problem.
Now I don't know if something is worn or ready to break, or if this was a one time failure because it was so frickin cold out.
Time will tell.