Why was the heater fan reversible?


The old and reliable.

Yard Art
Yard Art

Posts: 62

Joined: Wed Aug 02, 2017 11:17 am

Post Thu Sep 20, 2018 7:59 am

Why was the heater fan reversible?

I have been researching the archives regarding my heater switch operation which seems to be off in the center position, and a slow and fast fan position, both to the right and left of center. With direct and indirect labeled on the little bacolite switch tab (right and left of center).

The old forum topics seem to indicate the motor was reversible. Why was it designed that way? I guess I am just intrigued, I have not heard of a reversible heat/defrost fan motor before.....

I am running the old KB-7 cab and all the original devices on a 12 volt Chevy C-40 chassis. So I assume I will have to install resistors in my wiper and heater fan circuit so I don't burn up the 6 volt motors. I did install a resistor unit for my gauge cluster. The heater core and blower motor seem to work good. I have not tested the wiper motors yet.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Thu Sep 20, 2018 8:23 am

Re: Why was the heater fan reversible?

The heater fan was reverseable to provide the hottest air to the defroster or to the cab. On indirect (it drew air from the front and exited the back where it was picked up by the squirrel cage blower and onto the windshield. When on direct, it blew out the front and the defroster get the return air at the back to blow onto the windshield.
The defroster works regardless of which way the paddle fan is turning.
DON"T USE RESISTORs they don't cut voltage they resist current flow (not the same thing) Use a solid state voltage convertor to supply a 7.2 volt feed for your "6 volt" items. They are available from ebay and other places. You can buy one or have one for each item, just be sure to get one big enough to handle the current load you will be putting on it. Motors require more current to start than when they are running.

Yard Art
Yard Art

Posts: 62

Joined: Wed Aug 02, 2017 11:17 am

Post Thu Sep 20, 2018 12:48 pm

Re: Why was the heater fan reversible?

Thanks Cornbinder. I guess the converter unit is what I actually used for the instrument panel gauges. I got it from Antique Auto Garage on line.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Thu Sep 20, 2018 1:24 pm

Re: Why was the heater fan reversible?

You can get a 15 or 20 amp unit off E bay to power the wipers and heater fan, much better for them then a resistor which will limit the current available for starting and under load

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