Kool-a-matic fan replacement

[davidbrady]

If the NAPA is 1/3 hp at 3000 rpm's and draw's 18 amps, I'm saying use a larger rheostat inline to control the speed to a maximum of 1000 rpm's which will cut your power to 1/10 hp and your current to 6 amps. (Approximate numbers). IOW's, the rheostat (or wire wound resistor) will drop the voltage that the motor sees, but it has to be rated to handle the power dissipated across the rheostat/wire-wound resistor.

A quick search shows that the wire-wound resistor values are something like:
0.46 ohms, 50W
0.6 ohms, 22W
1 ohms, 16W

IOW's, don't run it at full speed!