The Stovebolt Site Forums The Shop Area The Electrical Bay Fresh Air Heater Motor

So I picked up a fresh air heater, over a year ago from a guy that had a bunch of stuff. It’s not much to look at, but I tested the heater core. Seems to hold vacuum well. And I hooked a 12v battery up to the motor and it sounds good and runs smooth.

This would be going in my 51 truck that was converted to 12v long ago.

How could I tell if the blower motor on this thing is 6v or 12v? Are there marking to look for? Some sort of other test I could do?

I thought if it was a 12 volt blower motor the two holes were the
motor mounts were a little bit off and the holes would have to be slotted on the heater body .also the motor wires may be cloth if 6 volt

There is a 12V motor that comes from most vendors, O'Reilly's, NAPA, Autozone...It fits well but end of motor is shorter and flat so the part that sticks through firewall is a little different looking. it has a slip on collar over drive shaft so it can be used in the stock squirrel cage fans. I bought from O'Reillys years ago for $31. O'Reilly auto Part # PM354 for $31 https://www.oreillyauto.com/detail/...998-chevrolet-venture?q=pm-354&pos=0

Go to Deves tech net site and he has an article rebuilding a delux heater that has a lot of imfo on the blower motors as he put a 12 volt motor inside a 6 volt motor housing .Not to say you want to do what he did but it shows a lot of the motor differences.

NAPA M6478 is a direct 12V replacement

I’m sure I could replace the motor. Is there a way I could tell whether my current one is 6v or 12v?

Hook it to a 6v battery and see if it spins at high speed.

Sometimes there is a 12 v or 6v stamped on the casing put up a picture maybe someone could tell.

If you run out of ideas and aren't hung up on being 100% original I have offered a 3 speed 12v motor in the freebies section. Used, of course but works. Not what I'd call whisper quiet but none of these are and when you bolt them to sheet metal you have a nice sounding board to boot.

Dumb question: how does the three speed wiring work?

Familiar with the concept of the two wire where you just have power and ground and a switch that adds resistance. Different style switch needed with your red/yellow/black motor?

One wire is gnd (BLK), one Lo hot (COLOR), one Hi hot (COLOR). Need proper switch to operate....or just use Hi'

The wiring/switch/rheostat, in general, depends on if resistor is in switch or in motor.

Actually it is a three speed motor. You use a 4 position switch...off, on1, on2, on3 (rotary) and the motor will operate at whichever speed you choose. As I recall on this one orange is low speed, red is medium and yellow is high speed. The motor is wound for 3 speeds. No resistor and no start nor run capacitor is needed. Just a plain old common three speed fan motor used in all sorts of applications. Very common in hang-down AC units with a cylinder type fan and also in heating units with a three or four bladed fan.

Standard Motor Products makes these four position heater blower motor switches which look period correct on our trucks:

HS-98

They also make an infinitely variable rheostat switch for both 6v and 12v systems. I like it on my heater because it lights up when you turn it on.

HS572 (12v)

HS-92 (6v)

www.ecatalog.smpcorp.com

I have the original 3-way switch (assume low speed, off, and high speed). I am wanting to wire up so that power is on only when ignition switch is on. I will be splurging on an original look AM/FM stereo that I want to wire the same. Did you wire up so heater fan shuts down with iginition switch off? If so, how did you wire it?

Wire it so that the hot wire going to the 3 way switch connects to the "on" side of the ignition switch. One post of the ignition switch is hot and the other side is hot only when the key is turned on...assuming you have the old simple 2 position ignition switch and a stomp starter. If you have the newer style ignition switch (which has on/start/acc then I'd connect the hot wire going to the 3 way switch to the acc post so it will be on either when the ignition is on or when the key is turned to the acc side.

It is the old 2 position. So the two wires (heater fan and stereo) would go to the hot key-on wire, but I would think I need a special connector to tap two wires into that hot wire. Do you know what connector I would need?

As long as you have room on the ignition switch post, you can just stack the connectors on top of each other. However...I don't know if this has been mentioned up until now but you do need to have a fuse in the wiring for the heater fan and the radio. Common ring terminal connectors is what I'd use to connect to the ignition switch.

Next question, if I hadn't exceeded my allocated amount. I converted vehicle to 12 volt. I bought the step-down 12 volt to 6 volt converter for heater motors. Just to test, I bypast the switch. Heater blower was running very slow, but worse yet, smoke started coming from the converter. The converter indicated which terminal was to battery so it should have been connected right. I don't get it all. I unhooked and then took a chance on 12 volt power to the blower. It blew like a mini tornado. If I had continued, would I have burned out the motor?
On a similar note. I have the original heater fan switch (I have seen from photos of other trucks). It has a spring in back along with a fuse that I tested is not blown. There is a small screw to connect a wire along with a male connector. I connected power to the screwed connector (assumed) and showed voltage. There was no power going to the male connector as I toggled through the switch while I had the ignition switch in on position. Maybe power wire should go on male terminal?

Yup.

I would say (not knowing anything about your particular motor) that you exceeded the amperage rating for the step-down converter. When you convert 12 volts back to 6 volts, you have to "waste" some energy that wants to be sent through the wires. It gets "wasted" as heat, plain and simple. So, you can forget using the converter you bought. You will need one capable of handling twice the amperage your motor was designed to use (for the sake of safety). In other words, if your motor normally uses 10 amps, you'll need a converter capable of handling 20 amps. That one will have a finned aluminum heat sink on it. It might look like this one:
https://www.amazon.com/Areyourshop-...;psc=1&smid=A38Z6HY60XAMH7&gQT=1 If on the other hand you bought one of the converters some people use for a fuel gauge, that one is only rated for 1 or 2 amps and that is why it is smoking.

Okay, so much for converters. The best of all worlds is you get a 12 volt fan (two or three speed is going to be the most pleasant to use) and a simple 3 or 4 position switch. Please go look in the Freebies section. You can see an honest-to-goodness American made heavy duty 12v three speed motor that is being offered for free (aside from cost of shipping which USPS Priority will be around $16).

I hope this helps. Your fan motor is currently a 6v motor and the only way to make it work safely on a 12v system is with the proper converter.

Here is another suggestion: remove the motor in your heater and compare it to the one I've offered in the Freebies section. If it fits and the shaft is long enough, please get the free one.

Another solution is to use a pulse width modulating power supply. I bought 2 of them from some Chinese company a year or 2 ago for less than $5. Look here for more info.

Down side is that it may inject noise into your radio.

NOTICE.......large edit above.

mea culpa

Good info. This is the one I tried using. Also, there is a single wire coming from heater motor. It looks to be four wires on the more heavy duty converter.

Joe, I'm not at all familiar with that voltage converter. It really isn't like any I've seen. Where did you get it? The best of the 2 and 3 speed fan motors will have 3 or 4 wires respectively. Those motors will be internally wired to run at the 2 or 3 different speeds and you won't need a voltage converter at all if you have a 12 volt system. On the other hand, if you have a 6 volt system, you will need a voltage converter that is capable of handling more amperage (I would suggest 30 amp at the least). The closer the amperage rating of the voltage converter is to the amperage consumption of your motor, the hotter the converter is likely to be. I understand this can be confusing. Please let us know your questions.

is the wiring cloth covered?

Thanks for all the responses. LMC sells the converter (for motors). Smoke came from that converter. Yes, there is a single cloth covered wire from heater motor (6 volt original). I gave it 12 volt power and it blew like a mini tornado. Someone here said the motor would burn up on 12 volt power. I would be inclined to buy the 30 amp rated converter if it solved the smoking problem.
Also, I have the original 3-way toggle switch with 2 connection points. I'm not sure how that would hook up to the converter and then to the signal cloth wire on the heater motor.

The 30 amp converter (DC to DC...12v to 6v) will be able to handle the amperage (current) requirement of your heater motor and should stop the smoking. That is assuming the heater motor is in good nick and doesn't have some internal short or something.

However only if you have a 2 speed (or 3 speed) motor will a multi-position switch be able to make it run correctly at different speeds.

Hoping not to be boring, but a 2 speed or 3 speed motor is internally wired to be that way. A 3 speed DC motor for example can run at three different speeds because of field (or maybe also armature) windings that are different. These windings produce different magnetic effects inside the motor and the neat thing about them is they are designed so that all you need to do is to connect 12v to one of the wires and the ground wire to a good ground connection. When that is done, the motor will run at that same speed without getting overheated. This is how the best Heat/AC motors are made.

The alternative is to feed a simple DC motor less voltage. That will reduce the speed of it. But if you are at the same time converting 12v to 6v, please remember you have to find a way to "waste" 6v at higher amperage. Electricity isn't like flour...you can't just measure out a half of a cup to get 50% less. You have to send 6v off into "wasted voltage/amperage" land and that creates heat. So even if you have a really well-designed voltage reducer you will also have the amperes to discard.

A 30 amp DC to DC 12v to 6v converter will have 4 wires if it is designed correctly. If it doesn't have 4 wires, then I doubt it will be able to handle more than 5 amps. There will be 2 black wires and two colored wires. You will send 12v positive and 12v ground in using 2 wires and you will get 6v positive and 6v ground out from the other 2 wires. And you'll be able to power a motor that will use 15 or 20 amps comfortably...but the converter will get hot and it will have an aluminum heat sink.

For decades the best explanation I've come up with is this: please think of voltage as the size of your arm. Think of amperage as the strength of your arm. Mama Cass's arms were probably twice as large as Chuck Connor's. Which one would you rather arm wrestle?