I thought I'd share a bit of info I picked up today from an extremely knowledgeable local mechanic who works only on pre-'79 American iron. He informed me that th '59-'62 cars use different blower motors depending on whether the car was air conditioned. For some reason, the motors in non-a/c cars rotate clockwise, while a/c cars rotate counterclockwise. He's seen a number of instances where owners bring him cars that have had their blowers replaced, and then claim the new one is not very powerful, only to find that the blower was replaced with the wrong one. So keep that in mind if you find yourself shopping for a blower motor.
Thanks David,
That's good to know!
Do or did the fan blades typically come with a replacement motor? Either way a different direction isn't going to be the most efficient.
Good to know! I'm planning on servicing my heater box in the fall.
This makes no sense
James,
Not that I disagree.
But, please elaborate - explain.
Have fun,
Steve B.
Can't you just reverse the polarity of a DC motor to have it match the direction that the fan is optimized for? So if the motor is spinning the opposite direction that is desired just pull the pins from the connector and swap them.
I don't have first-hand experience with this issue; it was mentioned to me in the context of "I'll bet you didn't know this" in course of discussing some a/c issues. But he did not think it made sense, either. He thought perhaps it had something to do with the ducting. But I have the utmost faith in this guy and his knowledge, as do a number of other members who are not on the forum. He only works on pre-'79 US cars, and has pretty much seen it all.
I'm no expert. but the blower motor has a squirrel cage fan inside the assembly.
There are fins on the fan that when spinning cause air flow.
If you simply reversed the wires, assuming that changes the direction of the fan, wouldn't the fins spin backwards, and not push air ???
Maybe the fan would then suck air out of the passenger compartment.
That would be nice while you cruise along in your Cadillac smoking your cigar, and the fan sucks the smoke out - LOL.
Wait, there is an easier way to clear the cabin, roll down a rear window, yep.
Have fun,
Steve B.
It depends on the type of motor if just reversing the polarity will reverse the motor. If its a permanent magnet type then yes its that easy but that isn't the most common design. Most designs both the rotor/armature/turning part and the field/housing/non turning part are electro magnets.
Its the relationship between the spinning and fixed parts that set the direction so in the case of a permanent magnet that part can't change so flipping the electric part changes that relationship so the direction changes. With both being electro you have to flip one section. If its a motor that is intended to be reversed the wires for both sections will be brought out so this can easily be done. If its not intended to be reversed the wiring will be internal so flipping the input won't change that relationship and the rotation won't change.
An example of this is starters. When you change a car from POS to NEG ground the starter doesn't spin backwards. On starters the connection between the armature and field is internal.
A regular propeller style fan blade will flow in different directions if you reverse the rotation. Depending on the exact design it may not be as efficient reversed but they will still flow decent reversed. The 'squirrel cage' fans don't work like that. If you spin them in the wrong direction the flow stays in the same direction but you loose like 75% of the efficiency and with some designs end up overloading the motor at the same time.
My guess why Cadillac would have had different directions likely had to do with the way the duct work laid out and possibly the back pressure. Adding more ducts and restrictions for the AC system may have required a different blade design to deal with the pressure. Some blade deigns only work with very low restrictions while others only work with restrictions.
Quote from: Gabe Davis on March 21, 2024, 03:46:53 PMCan't you just reverse the polarity of a DC motor to have it match the direction that the fan is optimized for? So if the motor is spinning the opposite direction that is desired just pull the pins from the connector and swap them.
If the motor has 2 wires coming out of it, then yes, the polarity can be reversed, but it also depends on how the motor is wired internally.
If the motor housing is not connected to the internal wiring, meaning that it's insulated, then it's really easy to reverse the direction by reversing the polarity. (All of the Japanese cars use this type of motor, I think it's referred to as an insulated ground circuit, which requires a separate wire for the ground circuit. American cars used to all use the chassis as the ground circuit.)
But most motors usually use just one wire at a time and the housing is grounded, one wire makes it rotate clockwise, the other counterclockwise, and the switch determines which one.
The field windings, (usually just 2) are each wound in opposite directions which is what sets the magnetic field that turns the armature. One winding is for counterclockwise, and the other is for clockwise, like a window motor.
Either way, only one wire is powered at a time, and the housing is the grounding point.
On a single-wire motor, you cannot "just" reverse the polarity to make it turn the opposite direction, because the circuit uses the motor housing as the ground path.
To reverse this type it would be extremely difficult, you would have to insulate the motor housing and use a second wire connection on the housing as the ground and/or the power source, and the original supply wire would have to be connected to a switch along with the new wire, and the switch would have to do dual duty, one side would supply power while the other side is connected to ground. It would have to simultaneously switch the power and the ground from side to side in order to change the rotation.
Vehicles from the 80's up used this type of switch and motor on the windows. I found that out while modifying my 88 Suburban to use a Cadillac window motor from the 50's, 60's.
I had to modify the switch as well to eliminate the alternating grounding circuit to work with the older design motor. It's not difficult to do, but you have to know how.
But to answer your question quickly, NO, it's not really a good idea.
Rick
I have run into this issue. Indeed there are two different blower motors available for '59-'62. One rotates CW, the other CCW. Otherwise they are physically identical. The motors are case grounded - meaning that a single wire provides voltage to the motor and the motor housing provides the ground. For that reason, as Richard points out, it is not possible to reverse the polarity. If my memory serves me correctly, the AC blowers rotate CCW When looking at the shaft/fan, and are difficult to find new. The motors that rotate CW are easy to find - even Rock Auto has them.
I can confirm that the fan blades are angled in opposite directions between my original AC car blower motor. And a replacement motor I bought several years ago.
I never really looked at these side by side. They are very different.
IMG_20240323_152149749.jpg
Are those two supposedly interchangeable? The right one looks like the 70's 80's style.
Basically a DC brush motor can be reversed if you
switch the 2 wires going to the brushes (leaving the
field the same). The problem is getting it apart.
A permanent magnet motor could be reversed if you
have facility to remagnetize it, otherwise brush
wires must be reversed. Since the neg is generally
connected to the case, reversing the external wires
works but will give you a hot case. Bruce Roe
Quote from: bcroe on March 23, 2024, 04:38:24 PMBasically a DC brush motor can be reversed if you
switch the 2 wires going to the brushes (leaving the
field the same). The problem is getting it apart.
A permanent magnet motor could be reversed if you
have facility to remagnetize it, otherwise brush
wires must be reversed. Since the neg is generally
connected to the case, reversing the external wires
works but will give you a hot case. Bruce Roe
Bruce,
Not sure I follow your wire swap. Correct me if I'm wrong, but doesn't the power path on a single-wire motor flow from the input wire, around the field windings, then to the positive brush, through the armature to the negative brush, then to ground at the housing/case?
Just swapping the two brush connections wouldn't have any effect on it that I can see.
Rick
You kinda have to know what sort of motor you are dealing with... permanent magnet, series wound, shunt wound, compound wound, commutative series wound? You can build a motor to be easy to reverse or almost impossible to reverse.
Quote from: Cadman-iacBruce,
Not sure I follow your wire swap. Correct me if I'm wrong, but doesn't the power path on a single-wire motor flow from the input wire, around the field windings, then to the positive brush, through the armature to the negative brush, then to ground at the housing/case?
Just swapping the two brush connections wouldn't have any effect on it that I can see. Rick
Rick, reversing the pair of wires to the brushes will
reverse the magnetic field in the armature, without
affecting the field (permanent, wound, series, parallel,
or compound). That is how a brush motor is reversed,
actually doing it could be a bit of a mechanical
challenge. 4 poles/brushes you move 4 wires 90 degrees.
Bruce Roe
Bruce, TJ,
Thanks for the input, I didn't think anything other than the typical 2 brush motor was used for a blower motor. That's what I was basing my comments on.
I know I mentioned the 80's design window motors, which are a permanent magnet type, (I refer to them as a pancake motor because of how they look, and are an insulated ground motor making it easy to reverse), the typical 2 wire 2 brush window motor, ( and antenna motors), from the 50's to the mid 70's used 2 field windings that were wound in opposite directions, and only one was used at a time with one or the other wire as input.
The only 4 brush motors I've ran into are starters and winch motors. The winch motors use solenoids to reverse the polarity to change the rotation direction.
But my knowledge is limited to just what I've I've learned from rebuilding what I have out of necessity.
I defer to your knowledge/experience/opinion on what it takes to do the aforementioned task.
Rick
On a side note here, the typical old-school 2 wire window motor, in my opinion, is not as powerful as the size makes it appear because it can only use one field winding at a time, whereas the later "pancake" 2-wire permanent magnet motor is half as large but just as powerful, making them fairly equal. The advantage of weight savings goes to the newer design, but in my opinion it sacrifices dependability and longevity.
The permanent magnet motor also has a built in circuit breaker for protection, but it can't handle a lot of current. The older motors don't have a breaker, they rely on the fuse in the circuit for protection.
That's something I learned from using the 56 window motors in my 88 Suburban. I expected much powerful operation from the swap, but they operate just the same.
The difference is in how long the older motors last.
Now I have a theory that the older motors will perform better if the switch and wiring were upgraded to a heavier gauge.
Unfortunately I had to use the original master switch in the Suburban in order to be able to still operate the rear windows from the drivers door. I only converted the front doors since they are used so much more.
So the master switch is an odd unit now, the 2 front ones now just switch 12v positive from one wire to the other for up or down.
However the 2 rear switches reverse polarity to the motors for up and down as designed.
To accomplish this I had to eliminate the ground circuit for the 2 front windows, otherwise it would simply short out the first time I used it.
I thought I'd throw this out there in case anyone ever decided to try it.
The older motors mount to the newer regulators exactly the same. If memory serves, I think I had to swap the bushing for the drive gear on the regulator so the gear shaft would fit. It's been 5 or 6 years since I did this, so I'm not positive now.
Another concern if you are swapping to the older, bigger motor is clearance issues.
I found out that the bigger motors, (I used the round ones instead of the rectangular type), just barely fit inside the door. There's maybe a 1/16" now between the motor and the door skin, whereas the pancake motor had at least an inch.
The upside to this swap is that I have not needed to replace any more motors.
Rick
Bruce and TJ,
Learn me somethin' here if you would. I'm trying to wrap my head around this. On a 2 brush motor with field windings that would typically be used for a blower motor, how does swapping the brush wires change the rotation?
As I understand it, on the armature the power goes in through one of the commutator bars, around the windings and back to the commutator bar exactly opposite from the input, then out through the second brush to ground. I think anyways.
Moving the wire for the brushes from one contact point to the other only makes the brush wires longer, there's still just an input and an exit brush, or a positive and a negative brush.
The power still flows through the armature exactly the same way, does it not?
The only way that I'm aware of to reverse a motor like this is to ground the original positive wire, and apply 12v positive to the case and the motor will run backwards, but I've only ever done this as a bench test. It's not something you'd ever want to do on the car
Now would changing the field polarity cause it to run backwards?
Please keep in mind I'm not an electrician, I know just enough to be dangerous as the saying goes.
Rick
You can't really make a blanket statement about how to reverse a motor without knowing what type it is and how to was constructed. I thought auto blowers were typically permanent magnets in which case it is as easy as reversing the input power.
If its something that has field coils then it depends on a lot of factors how you would reverse it. You can have a design that you just flip the input like a permanent magnet motor but you can also have designs where you have to be able to change just the field or armature. A starter is an example of that type, you can convert a car from pos to neg ground and the starter doesn't spin the wrong way.
You would use the different motor types depending on the requirements. Cost, longevity, starting torque, peak torque, do the torque requirements change depending on speed? Do you need it to change speed? Do you need it to regularly run in both directions? Is the torque requirement different in different directions? Do you care about efficiency? Size?
Quote from: Cadman-iac on March 24, 2024, 03:56:00 PMBruce and TJ, On a 2 brush motor with field windings that would typically be used for a blower motor, how does swapping the brush wires change the rotation?
As I understand it, on the armature the power goes in through one of the commutator bars, around the windings and back to the commutator bar exactly opposite from the input, then out through the second brush to ground. I think anyways.
Moving the wire for the brushes from one contact point to the other only makes the brush wires longer, there's still just an input and an exit brush, or a positive and a negative brush.
The power still flows through the armature exactly the same way, does it not?
The only way that I'm aware of to reverse a motor like this is to ground the original positive wire, and apply 12v positive to the case and the motor will run backwards, but I've only ever done this as a bench test. It's not something you'd ever want to do on the car
Now would changing the field polarity cause it to run backwards?
Rick
To reverse a DC brush motor, you must reverse either
the field or the armature magnetic poles. Reversing
the wires to the 2 brushes causes the current to flow
into the opposite commutator bar and in the opposite
direction around the winding, reversing the magnetic
field.
Reversing the stator magnetic field achives the same
thing, hard to do with permanent magnets. The motor
construction will determine the easiest way.
Some motors are built for easy reversal, one way for
a DC motor is with 2 stator windings wound in opposite
directions, either then feeding thru the brushes.
Some brush motors with no permanent magnets (electric
drill) are called universal motors, because they run
on either DC or AC. This works because reversing the
power does not reverse the motor. Bruce Roe
Quote from: bcroe on March 25, 2024, 03:03:32 PMTo reverse a DC brush motor, you must reverse either
the field or the armature magnetic poles. Reversing
the wires to the 2 brushes causes the current to flow
into the opposite commutator bar and in the opposite
direction around the winding, reversing the magnetic
field.
Bruce Roe
Bruce,
This is the part that is confusing me here.
Because the armature rotates, and each brush only contacts one or two of the commutator bars at a time, and they are 180° apart, if the positive voltage is going in one and out of the other, swapping the brush leads to move the positive side 180° from its original location, if the armature rotates 180°, then isn't that exactly the same as before you moved the brush leads?
Because the windings on the armature are not changed, the field generated in those windings is unchanged as well, and thusly, would still operate in the exact same way.
Or am I still missing something here?
I admit that it's been a few years since I've worked on a blower motor, and I don't remember if I'm getting a window motor and the blower motor mixed up, but on the older blowers, I thought they had field windings instead of permanent magnets, but my memory may be suspect here too.
If that's the case, I'll have to go take apart one of the blowers I'm thinking of and double-check myself.
Thanks for taking the time to edjumakate an old fart like myself.
Rick
To add here, I know that a window (and antenna) motor with field windings uses only one at a time, and each one is wound opposite of the other in order to reverse the magnetic field.
On a permanent magnet window motor, the power and ground wires are switched to change the rotation direction.
As I recall my 62 had a wound field wiper motor, but
the nearly identical 63 used a permanent magnet field.
If your brushes were feeding a couple slip rings (like
an alternator), the current would always flow the same
in the armature, rotating the magnetic field. But your
motor brushes contact a winding and generate a magnetic
field approximately half way between attracting one
field pole, and repelling the other. When the armature
turns enough to contact the next commutator bar, the
current flows thru a new winding that is positioned in
THE EXACT SAME POSITION as the previous winding was, so
it generates a magnetic field in the SAME position. The
armature rotates, but due to the switching action of
the commutator the magnetic field stays pretty much
in the same place. A generator does the same thing
in reverse, the generated power is connected at the
right time by the commutator, to give approximately
DC output.
An alternator is like an inside out generator, the
slip rings generate a fixed field in the rotor. An
alternating current is generated in the fixed outer
windings, and solid state diodes are used to get DC.
The diodes eliminate the heavy wear and radio noise
from arcing with brushes. The unit generates much
more energy per pound. But diodes are not as
efficient, you need to drive them with at least 16V
to get 14V out to the battery. This starts to look
pretty bad in a 6V system, 1/4 of of voltage lost.
Bruce Roe