2002 t800 blower!!

Is your fan speed control switch getting toasty?

Replace that switch and the wires, bout a 1 hr, 40$ fix (trucker ac, just search kw speeed control switch and pigtail) ooooor 800 for the full ac control panel (kw dealer price new 1.5 years ago, at 2002 it may be pretty well shot)

It could be the blower itself is also nearing dead causing it to blow the breaker

 

Blower motor probably pooched. Especially if there wasn't a filter on the inlet. Pretty common failure.

 

Disclaimer: DO NOT LEAVE IT LIKE THIS

To troubleshoot, run a good new power line direct from battery (fuse the red line at about 30A to a solid on off switch in the cab then straight to the blower, doesnt matter how janky, so long as all connections and switch are solid and new, recommend 14 ga and larger.

run 1 day, if no replication, i would say you likely have corrosion in the electrical panel at relay/fuse, at this age on a kw, its a common problem, the fix is to remove wiper reservoir and open up the panel from the back side and clean and repair every messed up wire there, be prepared for a grueling tedious job. BUT, first, if that fixes it, check your patched in new pigtail, that may not have good connections, that would induce higher load.


On the other hand, if you are lucky enough that it doesnt fix your problem, you know your blower however new is bjorked

 

Correct, high speed is basically full power

Note i said first if the direct line doesnt fix it, double check the pigtail you should have replaced with the switch, usually when the switch goes bad it crunchifies the wires, the pigtail has a new connector for switch + about 8" of new wire

 

Original blower box?

If so, Replace it (1000-1500 for the cores/box/blower, i like shoreline's its stainless), its not likely your issue as far as the electric switch blowing, but its likely contributing to clogged cores (no in line air filter on that vehicle year) which COULD lead to the blower having to work too hard, and if original, i guarantee you that the box is leaking air at almost every joint unless it was cleaned and painted monthly (or was 100% a desert truck)

Kw is also notorious for the freeze switch doing f-all, because it goes back to the dash unit to turn off the compressor, lazy fix for that is run the positive compressor clutch line back to the blower box to put the freeze switch directly on it (my compressor would run constantly, never kicking off)