Posted by Sherman in Idaho [162.158.104.119] on Friday, March 25, 2016 at 16:26:46 :
In Reply to: 6 volt heater on 12 volt truck posted by Jim in Litchfield Park [162.158.141.36] on Thursday, March 24, 2016 at 22:52:13 :
Scrounge up an ignition ballast resistor and use it to drop the voltage to the heater blower motor. In my experience, it's close enough to work just fine. The ballast resistor is beefy enough to handle the heat dissipation and with a typical blower motor it happens to be just about the right resistance to drop the voltage to 6 volts. If the voltage ends up on the high side, up to maybe 8 volts, that won't hurt anything, but it will give you more heat, which is always nice.
In technical terms, which you didn't want, a ballast resistor is about 1 ohm, and a 6-volt blower motor draws about 6 amps, so it gives you a 6 volt drop when running through a 1-ohm resistor. But just try it and you'll see it sounds right and runs right.