Posted by Sherman in Idaho [209.33.95.254] on Tuesday, January 06, 2015 at 23:34:24 :
In Reply to: Resistor for 6v heater to run on 12v? posted by CSCameron [184.101.181.75] on Tuesday, January 06, 2015 at 21:03:28 :
First try using an ignition ballast resistor -- whatever you have in your junk box. On the dodge heaters I've monkeyed with, that seems to provide just about the right resistance, and plenty of power handling capacity. They're about 1 ohm. You don't need to be super-accurate with the heater blower voltage. If anything, run it a little on the high side so you get more heat (there's never enough heat). Check the voltage at the motor with the resistor in series with motor, and if it's less than 8 volts, you're probably safe. You could even get fancy and use a /6 ballast resistor and a double-throw switch for a "hi" and "low" setting.
The kind of voltage reducers used with gauges either won't work or are overkill for this application.