Technical Whats the trick with old heater fans that blow the wrong direction ?

After being taken apart , cleaned and put back together , by me . Before i took this one apart i,m certain it was blowing through the heater and out the front. Now it,s sucking from the front and blowing out to the back. So i took it apart again and turned the guts 180 degrees but it,s still sucking instead of blowing. No, reversing the fan is fake news, the fan blades stay the same. Swapping wires on the battery poles does,nt make a difference. I,ve taken these apart before but this is the first one with such a problem. It spins great though after the cleanup .

 

If you can't find another fan blade that angles the other way, you could make a fixture that holds the hub of the blade, and has a guide so you could twist the 4 blades to the same angle opposite to the way they are now. Maybe with a torch applied to the twisted area.

 

Reverse the positive and negative feeds?

Feels like that should work on a DC motor.

 

Yes, reverse the connections. DC motors will reverse rotation with swapping positive and negative connections.

 

i wish id have said that !

 

Does the difference between positive ground and negative ground systems matter .
Just wondering .

Tommy

 

As in just pulling the brushes out of their little spring loaded brass guides and shoving into the opposite guide ? Thought i had done that. Try again then i suppose.

 

Assuming the fan is turning counter clockwise?
It appears the "pitch" of the blades would be the same in either mounting position. Did the wiring polarity get reversed in the rehab and testing?

 

No, just swap the two wires going to the motor.

 

No don't bother anything inside the motor. Just take your connections where they meet the wires of the motor and reverse or swap them.

 

Did you turn any of the motor parts around 180 degrees? If the brushes vs. magnets position is changed you can get that result.

 

i know on a starter if you reverse the polarity it doesnt change the rotation ! smart people can tell you why ........but i think on a fan it will change

 

I worked on British cars for quite a few years. They are almost universally 12 DC volt positive ground. I must have switched a hundred of them to 12v, ngstive ground and the heaters and starters all operated correctly except the horns went "KNOH"

 

On a common small permanent magnet motor reversing the electrical polarity will reverse the magnetic field on the rotor, making the magnets pull instead of push and vice versa, making it run the other direction.
On a universal motor such as a starter there are no permanent magnets, they are replaced with electromagnets. Reversing the electrical polarity will reverse the magnetic polarity of the electromagnets too, so instead of a south pole repelling a south pole you get a north pole repelling a north pole - the motor still runs the same direction.

 

It's probably for a car in the other hemisphere...

 

Just take the fan motor to your daily driver, touch the wires to the battery posts, see what happens.

 

Whenever I changed a car from positive to negative ground the heater fan ran in the original direction. So switching the wires will probably not change the direction.

 

Only on a motor with magnetic fields

 

Was it a positive ground originally? Or a 6 volt?

 

I had an old heater that switched the polarity at the switch. Flick it one way and it would blow towards the floor, flick it the other way, and it would blow up to the windshield. Would love to find another one.

 

G-son, More than likely something like that. Never had this problem before with cleaning and lubricating old heater fans.

Moedog07, Just an old 6 volt in a unknown heater. I should have used marker pen .

 

G-son has the right answer. A series-wound universal motor won't care about input power polarity. But you can reverse them. This requires changing the internal connections by changing the polarity connection on either the field OR the armature brushes, NOT both. This will reverse the rotation. There is one caveat attached though. Many of these motors are 'timed' (yes, just like gas-powered ones) for optimal operation in one direction, switching direction can cause them to run slower and hotter. On a fan motor it shouldn't make much if any difference.

 

Don't sweat it ()
this issue of yours has me reading the HAMB while waiting for my guest to arrive.

 

That won't do anything.

The fan blades are pitched the same, either way.

He'd need a reverse pitch fan assembly.

 

I'm guessing this has a wired field circuit. Most motors this age do. To reverse motor direction you have to either reverse the current flow in the armature or the field, but not both. When you reverse the input wires on this type of motor, it still turns in the same direction. It might be the easiest to do at the brushes, but you have to take the motor apart to see.

 

I literally spit beer out of my nose onto my keyboard when I read this. Shame on you, this burns! LMFAO!!!

 

He , he.

 

DC motors can change direction easily by simply changing polarity of the motor leads. The exception would be a 2 speed DC motor that has one ground, but two hots to change speeds from low to high.

 

Drive the car backwards really fast and the air should blow the other way.