Technical Arvin underdash car heater

So me and my boys decided to go out before the rain to tinker on the 49. We were clearing out all the old wiring and rotted ducks. I unhooked the heater hoses and noted it still has antifreeze in it and no leaks in the car; of course I didn't pressure test it either. I removed the heater from under the dash and was able to drain the rest out. It has a single wire to it. The fan turns, switch turns and clicks and has a good bulb in the knob. 1st question is the single wire positive or negative and would it be worth putting back in since it is a big unit and sticks down low?





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49' probably pos ground.

 

For what it's worth, I've upgraded a couple of old heaters with new 12 Volt motors, one was in a 49 Ford and the other a 1950 or so Pontiac "Harrison" heater, the other option is to get a BIG dropping resisiter and use the current motor. I used an aftermarket will fit fan switch on the Pontiac heater conversion so I have more than one fan speed. You need a good parts(wo)man to find one that will fit and have the right shaft size. Good luck, old heaters are just cool.

 

I am a fan of these old aftermarket heaters. The Hot Wave brand heater in my truck puts out plenty of heat. Very few cars and fewer trucks had a factory installed heater prior to the late '40s. Even the heaters that had the car manufacturer's name on them were usually dealer installed, as most optional equipment was back then. Harrison was/is part of General Motors. The same heaters they sold with the Chevy, Pontiac, Olds, etc. name on them were sold on the aftermarket with the Harrison name. There were dozens of brands of these aftermarket heaters. Most people bought one of the aftermarket heaters instead of buying a heater through the car dealer.

 

Had that version in a '41 GMC pickup, 6 volt and never cleaned or serviced. It defrosted the windshield and kept you warm in the 20 below Idaho weather. The wire hooks to the power supply & doesn't care about polarity. Don't exceed a 4 lb. cap on the cooling system, & don't use any kind of stop-leak **** in it.