1940 Hot Air wiring direction...

WarbirdPhotog

WarbirdPhotog

Senior Member
Hey all. Restoring my 1940 Ford hot air blower. The original wires are so faded and were cut so short that I can't tell what was power and what was ground.

Testing them out... Weirdly, no matter how I wire the two wires, the motor turns the same counter clockwise direction (which is the correct direction). I thought reversing the polarity through the motor would also reverse the motor spin. But not the case with this motor. So that didn't help!

I tried measuring the voltage output on both to see if one was drawing more than the other, meaning if they were wired the wrong way maybe there was a little more resistance. But they both show the exact same voltage rating.

One does sound a little smoother than the other, but it may just be playing tricks because the motor is spinning the same way.

So, it would appear that no matter how I wire it it correctly spins counterclockwise. But, I'm sure there was a proper way to actually hook these up and I don't want long-term damage from having a hooked up the wrong way. Anybody have any photos of their motor open like below showing which wire is which or know which side is positive in which side is ground?



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In order to change direction on a DC motor either just the field wiring gets reversed or just armature wiring.
 
Typically on a series wound dc motor the armature polarity is changed to change direction.
It looks like the brushes are about worn out.
 
Kurt in NJ said:
Typically on a series wound dc motor the armature polarity is changed to change direction.
It looks like the brushes are about worn out.
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It actually runs really well. The brushes are spring loaded so even if they wear, it keeps them firmly pressed on the armature.

But it's very confusing with the polarity not changing the direction.
 
I second that the brushes look well used . Understand how the spring works but when the carbon gets too short the spring pressure decreases increase resistance, heat and eventual ly it shorts out . A lot of amperage in a 6 volt system.
 
Ggmac said:
I second that the brushes look well used . Understand how the spring works but when the carbon gets too short the spring pressure decreases increase resistance, heat and eventual ly it shorts out . A lot of amperage in a 6 volt system.
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What would be the best way to replace the brushes in that case? Are they sold online in a way that I can just solder new ones?
 
Every hardware store should have a tray of miscellaneous brushes in the "Nut 'n Bolt" department. Take the old ones with you and match 'em up. Sometimes you can't find an exact match so you try to get something close and make 'em work. They are easily cut with a hacksaw and shaped with a metal file.
 
Most of the hardware store brush assortments are for 110 volt ac motors and have thin wires,look for dc motor brushes,there are some on amazon.
when I needed brushes for the tool post grinder I went to the vacuum cleaner repair store,he had a drawer full of unmarked obsolete brushes and I chose larger ones with wires that I liked the position and size then sanded them to fit.
 
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I’ve found new old stock brushes made for thepost war military jeep heaters work . You can usually find the motors 6 volt , cheap . I have a good working one in the shop . I’ll check tomorrow, if its still where I remember it , its yours . The whole motor.
Another alternative I’ve used ,is to just find the size carbon of your brushes and double deck them . Usually your old brushes need to be squared off on the ends to butt with the new brushes . That way no need to have them 6 volt only . Another option would be old train set brushes that you can still get new , or use to . The lionel oldies .
I have round carbon stock , think its 1/4 used for carbon arc stuff , it can be sanded square, messy but dooable . Anyway, I will check tomorrow on the jeep heaters motor . I probably have many 6 v heater motors.
Happy Holidays, Gary
Ps , carbon works but wears faster than the regular brush
 
Ggmac said:
I’ve found new old stock brushes made for thepost war military jeep heaters work . You can usually find the motors 6 volt , cheap . I have a good working one in the shop . I’ll check tomorrow, if its still where I remember it , its yours . The whole motor.
Another alternative I’ve used ,is to just find the size carbon of your brushes and double deck them . Usually your old brushes need to be squared off on the ends to butt with the new brushes . That way no need to have them 6 volt only . Another option would be old train set brushes that you can still get new , or use to . The lionel oldies .
I have round carbon stock , think its 1/4 used for carbon arc stuff , it can be sanded square, messy but dooable . Anyway, I will check tomorrow on the jeep heaters motor . I probably have many 6 v heater motors.
Happy Holidays, Gary
Ps , carbon works but wears faster than the regular brush
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Thank you so much! Let me know what you find.

Amazon does have quite a selection of carbon brushes, most of them though have the wire attached to the rear of the brush, which won't work in this situation with the spring. However, I did find these side mounted brushes. There's quite a few of them on Amazon. I could easily make these to size, but I don't believe there is wide as the ones I have now. So the question is, does the surface area the contacts the armature matter? Or as long as it makes a connection, it would work?

Example (see photo as well): https://www.amazon.com/dp/B0DK9BYVQ8?tag=atomicindus08-20
a8b3b04f3ca48c68df9ebfcd3438b5cd.jpg
 
Your wires exit the sides also . The springs would seat on the protrusion on the bottom of the Amazon picture. I’m pretty sure your lead is on the bottom of the brush, thats why I said they look worn .
 
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Ggmac said:
Your wires exit the sides also . The springs would seat on the protrusion on the bottom of the Amazon picture. I’m pretty sure your lead is on the bottom of the brush, thats why I said they look worn .
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The leads on these brushes are actually on the side, just like in the Amazon photo. In fact, looking at the size of the brushes, it's about .25 x .25 (or so) with the width. The Amazon brushes are .24 x .2. seems close enough? The length is no matter because the Amazon one is much longer than what I have now.
 
I found the jeep heaters motor, but I didnt have time to take the case apart . Tomorrow if you still need them . I’m glad you posted the size of yours.
Gray
 
Sorry to tell ya , my brushes are shorter than yours.
I’m curious, why do you want to reverse direction?
 
Ggmac said:
Sorry to tell ya , my brushes are shorter than yours.
I’m curious, why do you want to reverse direction?
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I don't want it to reverse direction. My original post was actually trying to figure out which of the two wires should be ground, and which should be power from the switch. I thought reversing the wires would reverse polarity, and cause the fan to turn backward which would be a clear sign that's the wrong way to wire it. But, no matter which wire you use for power or ground, it always spins the same way.
 
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