The Stovebolt Site Forums The Shop Area The Electrical Bay Heater Switch Wiring

I'm preparing to start the rewiring of my '47 3100. A number of other projects are "bundled" into this. One is the installation of a restored fresh air heater.

I've purchased a BWD S183 heater switch:
BWD S183 at O'Reilly

My question is which terminal on the back of the switch goes to the heater blower motor (the load) and which goes to the ignition switch (supply).

The heater and switch are 6 volt, the truck has been converted to 12V, so I have a heavy duty resistor to put in the line between the ignition and the this switch.

I could also use a recommendation for the fuse size (20 amp, 15 amp?)

Thanks everyone.

Bill

Well if it is an on/off switch it would not matter, The motor is grounded by it's sheet metal attachment or dedicated wire and the hot is broken by the switch. If it's a variable switch be sure motor is compatible. I don't see ANY heater on a dozen wiring diagrams for 47 I looked at. Obviously an accessory. Did find vague instructions to install heater as an accessory in 1951 car and truck accessory manual. Did not mention variable rheostat type switch, just on/off. Don't know history of your "heater" and "old switch" to tell if you have GM dealer accessory or other? Anyway the answer is that you will have the fused hot wire going into and out of switch, as you said. Either terminal. All a switch does is make/break contact between terminals. To calculate fuse: get watts or amps from motor markings or the internet and then calculate load/fuse/wire size. You can, of course, measure the current of the motor when it's running. BTW: 6V stuff needs larger wires than 12V.

The switch won't care which way you wire it. The switch with the speed control resisters won't care which way you wire it. Use the screw closest to the heater to run the heater. Use the screw closest to the drop resister to run the switch. Won't hurt a thing. Fuse according to the wire gauge that is on the motor and make all of the other wires the same. My best guess, 30 amp with 14 gauge wire. Put the fuse in front of the drop resistor. That will protect all of the parts you have in the system. Remember that fuse size is just a guess. Check the wire on the motor for sure. Look at the amp rating on the motor as well.

If the switch has a light in the knob, it may care which way you wire it.

Only if you don't want the light on all the time.

Not lit.

I would suggest fusing it at 14 amps. It shouldn't really draw more than 8, assuming it is 6 volt.

Thanks all! The contacts are close, so if the light misbehaves, I can easily reverse them.

I appreciate the help.