The Stovebolt Site Forums The Shop Area The Electrical Bay Voltage Reducer Placement (Heater Motor)

I bought part number EL135 from Jim Carter Truck Parts to step 12V down to 6V for the heater motor in a 1948 3600.

Which side of the heater switch should it be placed?

1.) 12V source to heater control switch

2.) Heater control switch to heater motor?

Is there a better choice for a voltage reducer?

I'd put that reducer (which looks OK) on the input side of the switch.

That resistor is intended to be bolted to sheet metal to dissipate the heat. That exact resistor costs around 3.50 at an electronics supply house.

truckernix,

What would be a brand name and part number for that resistor?

Thanks,

Wouldn't it make better sense to replace the heater motor with a 12V motor? I'm not sure of the current draw from the 6V motor, but think it's rather high therefore the resistor will get pretty hot. Be careful.

Actually in quantities of one about the cheapest you could find
them at someplace like Allied or Mouser is about five bucks.
All they are is a wirewound, aluminum housed, chassis mount,
power resistor. JC gives you all the specs that you need to
order one from any electronics supply house.
Here's one example from Vishay, but there are many others:
http://www.vishay.com/docs/30201/30201.pdf
If you threw it in with a group of other things on an order from
one of our old truck vendors it would come out about the same
as if you ordered one from an electronics supply and had to pay
the shipping for one item.
And you are correct Dave, picture a 50watt light bulb under the
dash. But it's even worse because there is no energy being
dissipated as light so it's all heat. That's ok if it's mounted
to a panel as a heat sink as mentioned earlier.

Denny G

Here is what I am talking about. Digi Key Pricing on Resistor

The question was: which side of the switch. TC is only one to answer. I would have said output side, but I don't think it would make any difference electrically unless the switch can only handle 6V. secondly, these resistors have heat sink fins on them and need to be places in fairly open air path, not tucked away. They will not start a fire.

Well most of these switches have a light in them. So if one wanted to place the resistor after the switch one would want to replace the bulb with a 12 volt bulb. I can't remember whether the light bulb is replaceable or not.

My original switches do not have a light bulb.

An original switch got quite hot (glowing hot) when I used the 6v heater without a resistor after converting a truck temporarily to 12v (back in the 70s). I just figured the switch would get less hot with the resistor before the switch.

Without a light it wouldn't really make a difference. I am surprised that your original survived on 12 volts. On six volts those resistors would glow. I discovered that the 6 volt replacements that i was able to buy melted with the 6 volts. I now only use it on high.

Roger that TC.

I failed to mention what fan switch I'm using... it is part number EL318 form JC also. This switch is three positions; 12V and does have a removable light bulb behind the knob.

With the information given here I have developed the following plan for a circuit.

12V Feed to http://www.ynzyesterdaysparts.com/index.php?_a=product&product_id=89"> Inline Fuse Holder then to the fan switch EL318.

From the switch to the voltage reducer EL135 mounted to an Aluminum heat sink then to heater motor.

Please advise of any concerns with this circuit. Thanks.

Perfect. Who cares if the bulb and resistor gets hot? Aren't we wanting heat?

red450,
I don't understand the comment from bartamos but yes, what you described should work fine.

Well, anyway Truckernix, Happy Birthday. Try to see the humor in life a little more.

Thanks for the happy birthday. I enjoy humor but I thought you were making a point that I missed, sorry.

Down here in AZ. there is a "cinco de mayo" celebration. But doesn't mean anything to me. But your birthday does. Enjoy it!!