VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt 1938 Heater Defroster wiring

Hello Fellow Members,
I own a 1938 Master Deluxe 4-door. I have the original heater and defroster and the original switches too. They are not wired up though and I think it's time. Here's the issue: the heater and defroster have one wire coming out of each of them but the defroster and heater switches have two positions and two terminals! How do they both get wired? Two wires combined into one?
Thanks for the help!
Jim

One wire goes frm the power sorce to the switch and another wire from the heater to the switch.

Thanks Gene! Why didn't I think of that? Senior moment I guess!

I would recommend that you do not wire those switches through the ignition switch. Those blower motors draw quite a bit of current and could overload the ignition switch.

Rusty! Where's the best spot to hook up for power?

On my ‘37 I took power from the ignition switch terminal that is always hot. That would be the terminal where the lead coming from the ammeter is connected.

I assume you are using these wiring diagrams.

Chevy wiring diagrams

For clarification since you both referred to connecting to the ignition switch, Rusty correct me if I'm wrong, Rusty is saying to connect to the non switched side of the ignition switch instead of the switched side. You don't want the amperage going through the switch.

While it can be connected to either side connecting to the side that is only hot with the switch on is adviseable....because there is no chance of the eletrical devises running or on my accident when engine is not running. This also makes it unnessary to turn of the device each time the engine is shut off which if not shut of could cause the battery to run down.

Is that not too much amperage through the ignition switch Gene?

No and that was the factory instructions when installing a heater.

I will defer to Gene’s recommendation. I have never seen a set of installation instructions.

I do not want to damage my ignition switch because Electrolok’s are getting harder and harder to find. I do have the add-on turn signals wired through the ignition switch. That is a load that never was considered in the design of the electrical system. My concern was that the combination of ignition, turn signals, and both blower motors would be too much for the contacts in the ignition switch.

I agree that not wiring through the switch means that you could leave the fan running when you stop the engine. In my situation I always check the ammeter after I stop the car. If the needle is not in the middle I check things. Also, on my car there is are lights in the knobs for the blower motor switches. They are on if a switch is in a run position.

I like the idea of a relay in this situation, especially if you have multiple accessories.
You can then have everything switched thru the ignition switch but the ignition switch only sees the current for the relay coil, rather than the full current of all accessories.

I wonder how it was wired in 1938? I definitely won’t go through the ignition switch. The relay sounds like a good idea.

As Tim noted, a relay is a great alternative. You can find 6 volt relays on Amazon.

They are not difficult to install. You do need basic electrical knowledge and skills. It is difficult to find relays with screw type terminals so you will probably need to install different terminals on your wiring. You will need to ground the coil side of the relay. The relay should be mounted so it does not bounce around behind the dash and potentially damage other wires or itself.

Here is what the '40-'48 heater instructions tells the installer.

When you add the defroster switch next to the heater switch you simply add a short jumper from the heater switch.

Just as Gene indicated.

Thanks! This is all very helpful.

how do you post a pdf or picture? I found something interesting to share about 37-38 heaters

I think I added the pdf?