Some great suggestions here -- thanks.
The switch did 'smoke' but it was probably due to some contaminant in it. Otherwise, it was just really hot with one of the exposed internal coil glowing.
I didn't like that observation especially as it would normally be mounted behind and through the dash.
The motor seems to spin ok once I put it back together. The bearings were reoiled, the brushes looked fine.
Thing is the motor does draw more amps if not spinning in its normal position: horizontal -- which it wasn't when on my bench --I had it propped up with it's hot water pipes holding it up, sort of on an oblique angle. I'm chalking it up to just an old motor with archaic bearings. The motor won't draw any more than 6.5 amps in any position.
Yeah, I did try to gang the two 1 ohm, 50 watt resistors in parallel (provides .5 ohm, 100 watts) and that did spin the motor really well, but it also made the rheostat switch get even hotter too ..the coils within were glowing pretty good. Again, the hot switch concerns me.
After doing some more testing I found that the resistor(s) increased in value as the temperature went up. This definitely had an effect on the output voltage, etc. If I was pursuing this, perhaps I should be looking for a 100 watt version??
So the truck is a 1st series Chev, but the recirc heater is from a '51 GMC. I purchased it at a swap meet some years back. This was to replace the original small heater that had no fan.
I yes, always provide appropriate fuses for my accessories.
