There is no logical reason a 6-V fan would turn slower at 12 V unless there are other factors, e.g., bad bearings or bad commutator.

 

I did hook it up to my 12vdc supply in the car and the fan turned, not fast but it did turn, maybe about 700rpm. I am thinking that it is not a high speed fan. I also cleaned the com and checked the brushes which had very little wear.

To get a pretty close RPM value, would be to rotate the motor shaft until you see ~6v generated on the leads, then measure the RPM.
Max.

 

!937, this is most likely a wound shunt field motor so the rpm is not going to be a direct ratio correlation to 6v and 12v voltage.
If you want to vary the RPM of a shunt wound motor, you need to keep the field constant.
Max.

 

!937, this is most likely a wound shunt field motor so the rpm is not going to be a direct ratio correlation to 6v and 12v voltage.
If you want to vary the RPM of a shunt wound motor, you need to keep the field constant.
Max.

Hi Max all I want to do is to put this 6vdc fan motor into my car that is converted to 12vdc

 

Does it have a two speed heater fan?
Also, it is now positive or negative earth? Most British cars prior to 1970 were wired positive earth.

 

I haven't read this thread from the beginning but why not use a 6V regulator?

 

I haven't read this thread from the beginning but why not use a 6V regulator?

Because the motor current is not yet known. It might end up a very warm regulator! But I suppose there would be a large fan in the vicinity to keep it cool. It might even help demist windscreen before the engine warms up.

 

Use a big TO-3 with a big heatsink over the fender well?

 

Or a switch mode 12V to 6V converter to limit waste power, aka heat.

 

Does it have a two speed heater fan?
Also, it is now positive or negative earth? Most British cars prior to 1970 were wired positive earth.

originaly the car was 6vdc positive earth my car now is 12vdc negative. This is the heater fan. Its a simple affair, run hot water through a radiator and put a fan behind it.

Or a switch mode 12V to 6V converter to limit waste power, aka heat.

I went for broke and connected the fan to my 12vdc supply. I put my meter in series and checked the amperage. 0.24 amps was the reading.

Because the motor current is not yet known. It might end up a very warm regulator! But I suppose there would be a large fan in the vicinity to keep it cool. It might even help demist windscreen before the engine warms up.

I have gone for broke and hooked up this 6vdc fam motor to my 12vdc supply. I hooked up my meter and measured 0.24 amps. Would a DC 12V To DC 6V 10A 60W Step Down Power Supply Converter Regulator Module work?

 

I went for broke and connected the fan to my 12vdc supply. I put my meter in series and checked the amperage. 0.24 amps was the reading.

That is really low amperage. I'm guessing this is just the motor spinning without the blower attached?

 

I have gone for broke and hooked up this 6vdc fam motor to my 12vdc supply. I hooked up my meter and measured 0.24 amps. Would a DC 12V To DC 6V 10A 60W Step Down Power Supply Converter Regulator Module work?

At that operating current, Sounds like you may not have any problem running at 12v!
You are not going to see x2 rpm if this is a wound shunt field motor.
Max.

 

At that operating current, Sounds like you may not have any problem running at 12v!
You are not going to see x2 rpm if this is a wound shunt field motor.
Max.

How do I tell if this motor is wound shunt field? I assume the field will be wound which is the case, instead of magnets.

 

It doesn't matter. It was designed to run at 6V, and you're going to run it at 6V with your 6V power supply.
At a guess, the current will increase as the commutator gets cleaned up after a bit of use.

 

How do I tell if this motor is wound shunt field? I assume the field will be wound which is the case, instead of magnets.

Only two leads,
If so to test for wound field., if not visible, short the two wires and try to spin the shaft, if resistance offered it is P.M. field.
Max.

 

It doesn't matter. It was designed to run at 6V, and you're going to run it at 6V with your 6V power supply.
At a guess, the current will increase as the commutator gets cleaned up after a bit of use.

Sorry for the confusion. This is a 6vdc motor that I want to run on12vdc

 

Also, if polarity is reversed, it will run in the same direction IF wound field.
Max.

 

Also, if polarity is reversed, it will run in the same direction IF wound field.
Max.

Good point. If it were permanent magnet, and you swapped the vehicle from positive earth to negative earth, the airflow would now be in the wrong direction.

 

That is really low amperage. I'm guessing this is just the motor spinning without the blower attached?

This was running with the fan attached. It is not a squirrel cage fan. Just a 4 blade 6" dia blade fan

 

Have you looked at a 12V replacement motor? Many of the old style fan motors were atached to a bracket with the same screws that held the motor together and since most car makers didn't make their own motors for things like this the motors were pretty much universal between brands of cars. So if this was mine I would just look at some of the places that sell old car replacement parts.

A lot of times the cars from that era used of brand heaters/defrosters too, since a heater was a dealer add on not something that came from the factory. Names like SouthWind come to my mind, but there were many more.