Converting a 6 volt heater to 12 volt

jbc

jbc

Senior Member
I have a 40 ford that has been changed over to 12 volts using an after market wiring harness with no heater switch. There's a 4 wire harness coming out of the heater and not hooked up. I assume it's a 6 volt. Do I try to find a 12 volt motor or is there a way to rewire this heater? Hi and low speed would nice, but not necessary.
Thanks
John
 
I got a 12 volt heater motor from NAPA. Be sure to get one that spins the correct way. The fan blades will tell you which way it goes.
 
most heater motors have the same bolt pattern, take yours with you when you go to buy one, most auto parts stores will have them or be able to order one for you
 
I'll check this morning. Do you know if the NAPA motors are wird for two speed?
John
 
I changed my 51 F-1 to 12 volts when I changed an engine. All I did was use a blower resistor out of a 70's GM car. Applied voltage to it and checked the output terminals until I found one with a 7 volt output and used it. That only gives you one speed but am sure one of the other outputs,(I think this resistor had 3 or 4 terminals with different volt output) would work with the proper switch, maybe a double pole double throw. It does have to be mounted in the air stream for cooling. For that I used a hole saw of the right size and made a hole in the heater housing and mounted the resistor where the fan would blow on it. It worked about 15 or so years that way with no problems.
 
I just bought a ceramic voltage dropping resistor from Speedway Motors and installed it ahead of the 3 position switch in my 48 chevy and it works great but remember these resistors do get hot so have it mounted in the open air. I did one car using the resistors out of a 67 ford but it has to be mounted behind the fan so air is drawn across the coils or they get red hot.
 
jbc said:
I have a 40 ford that has been changed over to 12 volts using an after market wiring harness with no heater switch. There's a 4 wire harness coming out of the heater and not hooked up. I assume it's a 6 volt. Do I try to find a 12 volt motor or is there a way to rewire this heater? Hi and low speed would nice, but not necessary.
Thanks
John
Click to expand...
I have been running my 2 speed 6 volt heater motor on 12 volts. It just runs faster (the same as running a 6 volt starter motor on 12 volts)
 
Thanks everyone, I'll try a drooping resistor. Does any one know how the 4 wires in the harness are hooked up?
John
 
I believe motors with the 4 wire leads are 2 speeds forward and 2 speeds reverse. I think the '40 used the reverse positions for the defroster(as did many other 1940's Fords). Most DC motors will reverse direction if you reverse the input polarity. Good luck.
 
Thanks again, One last question, does anyone have a schematic of the switch hook up and does anyone have a switch they would interested in getting rid of?
 
404665126.jpg

I bought a switch from Stacy Brown, antique auto supply in Texas
 
I found a ceramic reducer that is a little large, approx. 3/4" x 2.5 x 2.5". 12V in 6V out and has a tap for 10 amp and one for 3 amp. I mounted it clear of wiring etc but it does not get excessively hot. I did have a problem with the stock heater switch lighting until I realized I was using a 12v bulb instead of changing to a 6 volt. The heater/defroster works perfectly.

My .02

Fourdy
 
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