Variable speed fan switch?

Bamamav · Oct 14, 2017

I'm looking for some ideas for a variable speed switch for a heater fan. My fan motor is 6 volts, I plan on running it on 12 volts as long as it will last

, I'd like to put in some kind of voltage reducing switch to cut the volts down and slow the speed down. Looked on Mcmaster Carr's site, didn't really see anything I thought would work. Thought about using the dimmer part of a headlight switch, but not sure if it could handle the amps of the motor, which I figure are pretty small anyways. It's not like it will be running all the time in a daily driver, I figure it might not be used but a few times a year.

Any ideas? Cheap and easy?

[ddd

smallfoot · Oct 14, 2017

Something like this work?

https://www.amazon.com/MACs-Auto-Pa...8-1-fkmr1&keywords=12v+to+6v+reducer+resistor

MercuryMac · Oct 15, 2017

Bama, when I did what you're proposing, I had to learn a hard lesson first. The good news is, the motor lasts quite a long time, and it turns very fast. ----- The bad news is that the motor may turn backwards, [positive ground on most 6 volt vs. negative ground on 12 volt], and if you have a squirrel cage fan it's hard to tell what is backwards and which is forward, so you have a heater fan that sounds really good but doesn't do any dang good.
I lost a perfectly good girlfriend that winter before I figured it out. [cold car, not dorky personality, ------ I think.]

Anyhow check for direction of rotation. Good luck.

Bamamav · Oct 15, 2017

Smallfoot, that would cut down the voltage for sure,with a dpdt switch I could have two speeds, a low and a high, I might try that.

Mac, I have hooked it up both ways, it seems to blow just as hard both ways. I'm thinking it might be a flat fan instead of a cage.

No more than I drive it in real cold weather, I could do without a heater, but on some days, a defroster is just about a have to have thing. My heater was actually the defroster, I'm just going to hook a hose to one side outlet and leave the other open for floor heat.

Old Iron · Oct 15, 2017

The switch SM linked to works. I had a friend buy one and when he turned it on it got way to hot, I mean really, really, really hot.
I had him install a ceramic resister, in series, between the +12 volt wire and the switch and it works perfect now.