The Stovebolt Site Forums The Shop Area The Electrical Bay Advice on heater wiring and voltage reduction

Hi guys

I bought a refurbished 6v heater for use on my 12v system.

As expected on 12v the switch heats up but the fan works. I bought a voltage reducer 4R1%EMPI INC #9384. But when I add that in the line nothing works. Is this thevwrong choice in voltage reducer?



I just tried connecting the motor directly to the battery. Works fine but stops as I connect the voltage reducer inline. I wonder if the reducer has enough current ? Or if the motor has been changed to 12v?


Also where do you guys mount yours?

Cheers

I’d look closely at the motor and see if it is 12v.
If not swap in a 12v motor, search this section for info on 12v motors, easily found at local auto parts store and not at all expensive.

Oops, not sure where to get one in Japan, but you could buy one from the US

Thanks, is there a way to tell if it's 12v by looking at it? I
Guess if it runs ok and doesnt get hot it's 12v?

I ran a little experiment...

- with voltage reducer it won't start
- with 12v it starts and runs
- with 12v it starts then while spinning I quickly add in the voltage reducer and it runs very very slowly

So perhaps it is a 12v motor ? Or it's a 6v that s duff


I bought the heater on eBay from a guy who does heater restorations advertised as a rebuilt 6v..... certainly the switch is 6v.... but it arrived without the switch which he sent afterwards ...perhaps it's a mix up

Btw I have the '53-55 fresh air' Harrison system

Have you tested it off of a 6 v battery?
If it does not run it is not a 6 v motor.

Voltage reducers are essentially a resister.
All not only reduces the voltage it also reduces
the current flow (amps).

6 volt system components need more amps to
function. This is why 6 volt wiring is made with
heavier gauge (thicker) wire.

So when you get the motor running on 12 v then
adding the reducer it keeps running because the
motor has enough momentum to keep moving
with reduced current flow. Indicates that you have
a 12 v motor. In the absence of you testing the motor
on a 6 v battery. Jeffrey

Searching on that "voltage reducer" number what I find is a 50 watt 4Ω resistor.

It's not a fancy part, just a resistor.
Check it with a multi meter and see if it has about 4Ω resistance. If it has lots and lots of resistance, or an open circuit, it may be burned out. If it checks out at 4Ω then it works, and perhaps it's not the right value for what you're trying to do.

A 12V motor will run fine on 6V, but it'll run slow, as if you have the fan switch set to "low". I presently have a 12V heater blower motor in my 6V truck, works just fine, but will work better when I upgrade the rest of the truck to 12V.

A 6V motor will also run on 12V, but will run fast and won't last long.

Take the motor out if necessary and get a look at it, may say what voltage it is on the side, or a part number and you can look up what voltage.

If it is 6V motor then you need a resistance large enough to drop the voltage measured at the motor to 6V.
Or just swap the motor out for a new 12V motor, best option in the long run.
https://www.stovebolt.com/ubbthread...6055/Easy/cheap_heater_blower_motor.html

In any case the voltage at the fan motor should be 6 or 12V to suit the 6 or 12V motor, what do you measure?

Try running two of those resistors, connected in parallel. That will cut the resistance in half and double the current capacity. The motor doesn't care how it gets its current and/or voltage- - - -it just requires enough of each to run at the right speed. Placing the resistors inside the air box so the air from the fan blows over them will help to keep them cool. Just use a piece of non-conducting material like Bakelite to mount them onto the air duct.
Jerry

You need a 1 ohm 50 watt resistor. that will run the heater correctly if the motor is good. Four ohms is way too much resistance. Nominally that motor should draw around 6 amps so a 1 ohm resistor will be dropping around 6 volts.

Hi guys I got in touch with the seller and he said it maybe a 12v motor and that the switch (that he later sent me separately) should therefore have been a 12v switch not 6v. He's sending me the right switch.

Hopefully that'll fix it

Cheers
Mike

The switch on high wouldn't care much, or at all, if it's 12V or 6V.
The lower speed settings, resistances, may be different? But I've used old aftermarket 6V multi speed fan switches on my trucks with 12V without a second thought, and no troubles.