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I'm in the process of putting a fresh air heater in my '53 which has been converted to 12V by a previous owner.

Before I put anything in, I'm bench testing all the electrical stuff with a 6/12 volt battery charger.

The blower motor is an original 6 volt, and when connected up to a battery charger (6 volt setting), it runs great.

Then, using jumper wires, I put the switch I bought from Chevy Duty and the voltage reducer from 5th Ave. in line between the charger and the heater. I get one speed---ultra slow. None of the other switch settings work, either on 6 or 12 volts. I then took the reducer out of the loop and used just the switch on 6 volts. same thing. I then took the switch out of the loop and used just the reducer on 12 volts and then all I got was a humming sound from the motor.

What am I not getting here? Could both the switch and reducer be defective????

Anyway, on the back of the heater switch there is a coil of wire around some sort of insulator. What is that all about? Is that a built in voltage reducer? It got red hot when I tried other settings other than low. That's not normal, is it? Am I correct in assuming that the incoming line from the ignition goes to the terminal with the coil, and the outgoing line to the heater motor goes on the terminal without the coil?

Thanks for any advice.

Therapy,
The first thing I would do is get a good battery instead of the battery charger. You may not be getting enough amps. to run the resister and motor.
The coil on the back of the heater switch I believe is the old rheostat that was used.
I would opt. for using a relay instead.
Good Luck
Paul

The coil on the switch reduces voltage to change the blower motor speed. One position of the switch should have almost no resistance and the other should have some. Of course on "off" there should be no continuity.
I agree you should be using a battery instead of a charger.

I went ahead and mounted the heater and wired in a switch I found that looked heavy duty. The metal coil was surrounded by the porcelain insulation, instead of the metal being wrapped around the porcelain itself. This setup seemed safer in my opinion. Not knowing the voltage of this particular switch, I put the reducer between the ignition and the switch. When I turned the system on, It worked!!! However, I feel that the blower still runs a little slow, even on high.

Now for the kicker. I mounted the reducer in the engine compartment on the firewall due to the heat buildup. Boy did that sucker get hot! I couldn't even touch it with my bare hands. It even started to melt the insulation off the wires attached to it! I'm seriously thinking of just doing away with the reducer and running the motor on low. Low speed on 12V is just a little faster than High speed on 6V so I shouldn't burn the motor out too soon, right? Hey, I'm just an electrical novice, but I'm willing to learn. I just don't want to toast my truck!!

If I blow the motor, I'll go with the 12V replacement from Grainger, but I'll have to find a different blower wheel to accomodate the smaller shaft diameter. Anyone know of a source for either the wheel or a shaft adapter? I've asked about shaft adapters, and just gotten some blank stares.

Thanks for any and all help/advice

I replaced my 6V motor with a 12V motor from Chev's of the 40's. The replacement fits in the old 6V casing but you need to remove everything from the old casing. The shaft mounts just right and my replacement switch gives different blower speeds.

Those voltage reducing resistors are consuming a lot of amps and are dangerous.

shoeless

I just finished mounting the Grainger 12 volt motor in my fresh air heater.

To make the shaft adapter, I used a piece of copper tubing with an outside diameter of 5/16" and an inside diameter of 1/4". The copper tubing was about one inch long. I had to sand down the outside of the tubing a bit to get it to slide into the fan shaft hole. I also had to run a 1/4" drill bit down the inside of the tubing to get it over the new motor shaft.

Only other thing I did was to drill through the tubing where the fan set screw goes so the set screw would bottom out on the motor shaft and keep everything in place.

I have always had trouble trying to run the six-volt motor with the resister. Just easier to change the notor to twelve volt and eliminate the resistor.

I wonder if I ran the resistor in line to my horn if it would make it sound better?