Electric fan puller or pusher

[WZ JUNK]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

[1FATGMC]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

Just have Jerry drive in reverse, that should solve the problem .  I know you are tired and that isn't funny .

Seems like I had one where the instructions told you how to take care of that, but I might be wrong.  I'm wondering reverse the polarity of the wiring and reverse the blade on the shaft?

Don't attempt this without some input from someone else  :?

Good luck,

Sum

[tomslik]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

straight blades or are they curved?

[unklian]

How many wires coming off the fan ?

[HOTRODSRJ]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

Which Flex unit is it?  If it has a shroud like the black magic (with encased shroud)....the blades are only made to suck (with the leading edges or curved in the middle hump) rotating in that direction....so if it's running backward...then the polarity of the motor leads is reversed.

[WZ JUNK]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

Which Flex unit is it?  If it has a shroud like the black magic (with encased shroud)....the blades are only made to suck (with the leading edges or curved in the middle hump) rotating in that direction....so if it's running backward...then the polarity of the motor leads is reversed.

210 Puller   http://www.flex-a-lite.com/auto/html/low-profile-electric.html
I am wondering if I reverse the leads, how much air it will move?

[tomslik]

Flex Lite fan arrived yesterday.  Finished installation and checked circuit this afternoon.  Difficult installation.  Everything works fine except the fan pushes instead of pulls.  When I hold a piece of paper to the fan that is mounted on the back of the radiator (the side towards the engine) the fan is blowing the paper forward toward the radiator and the front of the vehicle.  I am tired, not very happy, and not thinking clearly.  Did they send me the wrong fan?

John

Which Flex unit is it?  If it has a shroud like the black magic (with encased shroud)....the blades are only made to suck (with the leading edges or curved in the middle hump) rotating in that direction....so if it's running backward...then the polarity of the motor leads is reversed.

210 Puller   http://www.flex-a-lite.com/auto/html/low-profile-electric.html
I am wondering if I reverse the leads, how much air it will move?

wz, i AM suprised you haven't tried it yet...
doubt it gonna hurt anything, at least it never has for me..

[HOTRODSRJ]

210 Puller   http://www.flex-a-lite.com/auto/html/low-profile-electric.html
I am wondering if I reverse the leads, how much air it will move?

John.....these fans are only made from a shroud/fan blade design to pull. So, if the blades are running the wrong way the correct way is to reverse the leads on the fan and it will deliver the specified CFMs.  Are you sure that you have followed the directions for the relay/motor interface.....but it's pretty easy just to swap the leads and go! No biggie.

Let's us know how it all works out for you?

[BFS57]

Hello;
Exchuse me if I step in here a bit. The blades on the fan really don't have too much to do with the direction it spins! Yes, certain blades do certain things but if they spin one way, they blow, if they spin another way, they suck!
I just changed the wires on mine and it went from pusher to puller! I see fans that are either and are made with that in mind.
My thought is that you should contact Flex-A-Lite technical and ask a few questions about the model you have.
Bruce

[WZ JUNK]

Hello;
Exchuse me if I step in here a bit. The blades on the fan really don't have too much to do with the direction it spins! Yes, certain blades do certain things but if they spin one way, they blow, if they spin another way, they suck!
I just changed the wires on mine and it went from pusher to puller! I see fans that are either and are made with that in mind.
My thought is that you should contact Flex-A-Lite technical and ask a few questions about the model you have.
Bruce

Well, I did call the manufacture this morning.  The tech guy would never say that the fan would work as good in either direction but he did say to reverse the motor leads and I did.  It was wired according to their diagram as I checked to make sure.  It now is a puller and it moves a lot of air.  Maybe not as good as it would if it was the right setup but I do not know that and I think it is moving plenty air to get the job done.  Time and hot weather will tell.

Thanks for the help.  I will try to remember to update this later if it does not cool in hot weather with the air on.

John

[HOTRODSRJ]

John,..... I assure you that the motors on these fans are simple DC motors that run as good in one direction as the other...they really don't care....so I don't know what's up with directions being wrong...and/or the leads are colored wrong or whatever...but it really doesn't matter.  The fan will work at the rated specification either way.  So...enjoy.

A clarification about my comment about the blades/shroud combo and why it DOES or at least COULD make a difference which way the blades spin for MAXIMUM output.  SIMPLE flat blades with a equal pitch throughout the blade length from both sides can be reversed and used that way with no penalty in CFM production as pointed out.  

But, for example.....if you think the ever popular Spal purported "straight-bladed" fans are simply reversable by swapping leads and plug and play...you are wrong at least from an airflow perspective.   They have a slightly "off-pitch" designed blade from one perspective that makes their direction imparitive to produce maximum CFMs. Note the difference in part number here for "pusher" vs "puller".  http://www.spal-usa.com/fans/automated/tech_sheets/2041-2055.pdf

Also in the same matter, "skewed" blade designs will NOT produce the same amount of air one way...and then simply reverse the leads of the motor and produce the same the othe way.  Here is a classic "skewed" design that if you want to reverse the direction of the fan...then you have to turn the blades around too.



These type of "skewed" blades are designed for the leading edge of the blade to turn in the clockwise direction (as viewed from this side) and would lose about 30% of their output by simply reversing the leads.  All bi-directional skewed bladed fans instruct you to not only reverse the leads, but turn the fan assembly around too for puller vs pusher operation.  

Just a clarification.

[PeterR]

The overwhelming majority of DC motors are optimised to run in one direction.    In order to negate the effect of rotor winding reactance, the brushes not are mounted at the true symmetric point, but advanced slightly.  It has some similarity to the ignition being advanced on a gasoline engine.

Even where DC motors are used in applications where they are required to be reversed, such as electric winches or garage door openers, they are still optimised for the high load direction and if they operate at lower efficiency in the low load direction it does not matter.

Any person doubting this only has to take a bare windscreen wiper motor, and run it first in the design direction then backwards by reversing the connections.   You will not need a fancy optical tacho to pick up the difference in speed, it will be quite apparent by the sound from the running motor.

In the case of fan motors, the manufacturers may make the motors "straight up" to save the need to stock different models, but I suspect they try to achieve maximum efficiency and if that is the case the motors will be designed for a particular rotation just like the curved blades.

[HOTRODSRJ]

The overwhelming majority of DC motors are optimised to run in one direction.    In order to negate the effect of rotor winding reactance, the brushes not are mounted at the true symmetric point, but advanced slightly.  It has some similarity to the ignition being advanced on a gasoline engine.

Even where DC motors are used in applications where they are required to be reversed, such as electric winches or garage door openers, they are still optimised for the high load direction and if they operate at lower efficiency in the low load direction it does not matter.

Any person doubting this only has to take a bare windscreen wiper motor, and run it first in the design direction then backwards by reversing the connections.   You will not need a fancy optical tacho to pick up the difference in speed, it will be quite apparent by the sound from the running motor.

In the case of fan motors, the manufacturers may make the motors "straight up" to save the need to stock different models, but I suspect they try to achieve maximum efficiency and if that is the case the motors will be designed for a particular rotation just like the curved blades.

Hey Peter...good info ....and I agree....I have seen alot of DC motors that are "rotation direction specific" for optimization (mostly in aircraft slaved motors in my experience).  However... I have had several conversations with Spal, Derale (esp these guys) and Hayden engineers that choose these motors specifically because they are "multi-directional" and lose no "working ability" running in either direction...again according to them.   I have to take their word for it...as designs of these can vary. But, these are pretty simple designs and relatively inexpensive motors and I have tested several multi-directional fans in a "airflow box" and they perform (CFM and RPM wise) almost exactly the same in either direction.

[PeterR]

If the fan manufacturers have indicated the motors they use are made "straight up" then they will not lose "working ability" one way or the other, it just means they will not be as efficient as if made for a specific rotation.   Likely they buy in the motors from a manufacturer that makes them bi-directional to be as universal as possible.  

DC motors used in automobile OEM applications are biased, but as they are built for a specific application it is not a big deal to have them optimised for direction.

[BFS57]

Hello!
Great Discussion you all! I have a set up in my '32 with a Walker radiator and a "Cooling Components" Fan shroud and fan. When I first got the car, I had cooling problems! One day, at the NSRA nats here in Florida, I was walking by the Walker truck and saw my combination on display. I turned on the switch to see how the fan worked and was almost blown over by the amount of air it was moving! Same set up, I remember that mine was no where this powerful! That started the wheels spinning in my brain why didn't my fan move this amount of air?
I started checking all around to find that (long story short) There was a insufficent ground! After I got proper grounding, my fan put out so much that I could hardly believe it! Hot days here in Florida and my Vicky never gets above 180 degrees even idling in traffic!
What I am trying to say here is the best electric cooling fan made won't work properly if proper connections and grounding are not done right!
I put heavier gage wire to feed the motor as well as assured a very good ground and it all makes it work like it should!
Bruce