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

Discussion in 'The Hokey Ass Message Board' started by 34 GAZ, Dec 25, 2021.

  1. After being taken apart , cleaned and put back together :eek::rolleyes: , by me :oops: . 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 :D . FAN,.jpg FAN.JPG
     
    kadillackid likes this.
  2. Lepus
    Joined: Nov 18, 2016
    Posts: 450

    Lepus
    Member

    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.
     
    hotrodjack33 and 34 GAZ like this.
  3. Reverse the positive and negative feeds?

    Feels like that should work on a DC motor.
     
  4. 52HardTop
    Joined: Jun 21, 2007
    Posts: 1,078

    52HardTop
    Member

    Yes, reverse the connections. DC motors will reverse rotation with swapping positive and negative connections.
     
    49ratfink, Boryca, tiredford and 5 others like this.

  5. buick bill
    Joined: Dec 18, 2008
    Posts: 856

    buick bill
    Member
    from yreka;ca

    i wish id have said that !
     
    tiredford and 34 GAZ like this.
  6. Does the difference between positive ground and negative ground systems matter .
    Just wondering .

    Tommy
     
    34 GAZ likes this.
  7. 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.:oops:
     
  8. Moedog07
    Joined: Apr 11, 2011
    Posts: 506

    Moedog07
    Member

    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?
     
    34 GAZ likes this.
  9. bigdog
    Joined: Oct 30, 2002
    Posts: 761

    bigdog
    ALLIANCE MEMBER

    No, just swap the two wires going to the motor.
     
    XXL__, Elcohaulic, dearjose and 3 others like this.
  10. 52HardTop
    Joined: Jun 21, 2007
    Posts: 1,078

    52HardTop
    Member

    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.
     
    Elcohaulic, 34 GAZ and Carter like this.
  11. seabeecmc
    Joined: Jan 28, 2005
    Posts: 1,185

    seabeecmc
    ALLIANCE MEMBER

  12. G-son
    Joined: Dec 19, 2012
    Posts: 1,275

    G-son
    Member
    from Sweden

    Did you turn any of the motor parts around 180 degrees? If the brushes vs. magnets position is changed you can get that result.
     
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  13. buick bill
    Joined: Dec 18, 2008
    Posts: 856

    buick bill
    Member
    from yreka;ca

    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
     
    34 GAZ likes this.
  14. 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"
     
    bchctybob, BradinNC, da34guy and 26 others like this.
  15. G-son
    Joined: Dec 19, 2012
    Posts: 1,275

    G-son
    Member
    from Sweden

    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.
    [​IMG]
     
  16. winduptoy
    Joined: Feb 19, 2013
    Posts: 3,316

    winduptoy
    ALLIANCE MEMBER

    It's probably for a car in the other hemisphere...
     
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  17. Just take the fan motor to your daily driver, touch the wires to the battery posts, see what happens.
     
    jim snow and 34 GAZ like this.
  18. oldolds
    Joined: Oct 18, 2010
    Posts: 3,407

    oldolds
    Member

    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.
     
  19. theboss20
    Joined: Dec 30, 2018
    Posts: 274

    theboss20

    Only on a motor with magnetic fields
     
    34 GAZ likes this.
  20. Moedog07
    Joined: Apr 11, 2011
    Posts: 506

    Moedog07
    Member

    Was it a positive ground originally? Or a 6 volt?
     
    34 GAZ likes this.
  21. goldmountain
    Joined: Jun 12, 2016
    Posts: 4,442

    goldmountain

    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.
     
    lothiandon1940 and 34 GAZ like this.
  22. 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 .:oops:
     
  23. 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.
     
  24. Moedog07
    Joined: Apr 11, 2011
    Posts: 506

    Moedog07
    Member

    Don't sweat it (;))
    this issue of yours has me reading the HAMB while waiting for my guest to arrive.
     
    buick bill and 34 GAZ like this.
  25. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,263

    gimpyshotrods
    ALLIANCE MEMBER

    That won't do anything.

    The fan blades are pitched the same, either way.

    He'd need a reverse pitch fan assembly.
     
    clem, 34 GAZ and winduptoy like this.
  26. jaracer
    Joined: Oct 4, 2008
    Posts: 2,417

    jaracer
    Member

    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.
     
    gimpyshotrods and 34 GAZ like this.
  27. I literally spit beer out of my nose onto my keyboard when I read this. Shame on you, this burns! :D:D:D LMFAO!!!
     
    pirate, BJR, 34 GAZ and 3 others like this.
  28. tommyd
    Joined: Dec 10, 2010
    Posts: 11,946

    tommyd
    Member
    from South Indy

    He , he.
     
  29. 1971BB427
    Joined: Mar 6, 2010
    Posts: 8,717

    1971BB427
    Member
    from Oregon

    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.
     
    34 GAZ likes this.
  30. spanners
    Joined: Feb 24, 2009
    Posts: 2,073

    spanners
    Member

    Drive the car backwards really fast and the air should blow the other way.
     
    buick bill, kidcampbell71 and 34 GAZ like this.

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