I have a electric fan in an old truck that it turns out is pushing rather then pulling.

Pulling it out and reversing the blades would be a PIA. So I tried reversing the wires and the motor does run the other way (blows the way I want).

So, is there some problem with reversing the wires?

I'm interested to know this answer. My shop teacher in HS always told us "no". I have a blade grinder that runs either way and has a two way switch. Are there electric motors that are made to run both ways?

I believe you would need to both reverse direction of the motor and flip the fan blade for it to be correct when wanting air to move properly in the opposite direction.

Electrically the motor doesn't care. Many times the blades aren't very efficient if they aren't turned around.

I don't understand some of these blade direction comments. If you reverse the direction of the motor AND turn the blades around, the fan is going to move air in the same direction it did before the changes.

quote:

Originally posted by Lenny5160:
I don't understand some of these blade direction comments. If you reverse the direction of the motor AND turn the blades around, the fan is going to move air in the same direction it did before the changes.

For my part I answered the question he asked, (which doesn't happen a lot on here LOL) but told him why it wasn't a good idea.

From my experience, no worries on the electric motor spinning the opposite direction for the fan. Most manufacturers want you to flip the blade over though so it pulls/pushes the correct CFM of air.

quote:

Originally posted by Lenny5160:
I don't understand some of these blade direction comments. If you reverse the direction of the motor AND turn the blades around, the fan is going to move air in the same direction it did before the changes.

Most blades have a curve to pull or push by design. When you spin it backwards the blade is less efficient and moves less CFM. Thats why most are labelled puller or pusher so you know which side of the radiator to mount them.

The motor doesn’t care just like the motor on an overhead room fan can be flipped to run in either direction.

DC motor does not care what the direction it's turning but the blades on the fan are a different shape/angle, either designed as a pusher or a puller

As stated above, the fan portion needs to be flipped to work as designed otherwise you will not get anywhere near the air flow that fan blade was designed for.

quote:

Originally posted by TOP38:
As stated above, the fan portion needs to be flipped to work as designed otherwise you will not get anywhere near the air flow that fan blade was designed for.

Unless it was wired wrong from the start. Put a piece of paper on the front of the radiator and see if it gets stuck to the radiator. Fixed a car last year that was wired wrong and couldn't believe how fast it cooled down after it was wired right.

quote:

Originally posted by 369dragster:

quote:

Originally posted by TOP38:
As stated above, the fan portion needs to be flipped to work as designed otherwise you will not get anywhere near the air flow that fan blade was designed for.

Unless it was wired wrong from the start. Put a piece of paper on the front of the radiator and see if it gets stuck to the radiator. Fixed a car last year that was wired wrong and couldn't believe how fast it cooled down after it was wired right.

Good point, Greg check the fan blade, it's pretty obvious which way it should turn for the right air flow.

too lazy to read al replies/ Flip the blades is all you need to do. Fan is stupid and has no idea which way air moves. 12v switching wires nothing. or 220 yes it reverse motor not on 12 and only 110 I have seen do so required switching wire in motor it self. Cieling fans have switch which essentially changes wiring for motor.

Most all 12v fans are super easy to switch . Normally E clip or similar and flip the over. It is angle of blades and which edge cuts air that decides flow.

quote:

Originally posted by wideopen231:
too lazy to read al replies/ Flip the blades is all you need to do. Fan is stupid and has no idea which way air moves. 12v switching wires nothing. or 220 yes it reverse motor not on 12 and only 110 I have seen do so required switching wire in motor it self. Cieling fans have switch which essentially changes wiring for motor.

Most all 12v fans are super easy to switch . Normally E clip or similar and flip the over. It is angle of blades and which edge cuts air that decides flow.

12v switching wires does nothing??? Maybe read up a little on dc motors before you say such things. Reversing the polarity of a dc motor reverses the direction anda dc motor runs. Reversing the connection of a 220 volt motor doesn’t make it run backwards necessarily, depends on single phase or three phase motor. Three phase motor you switch two of the phases to reverse it and single phase motor you only switch the start windings. I am sure I left a few details out but you get the point it’s not as simple as you make it sound for a 220 volt motor.

A note about DC motor direction and polarity. Power windows operate by switching polarity, one way is up, the other way is down, the design of the switch swaps the motor polarity.

Looks like a few guys got it right.
Yes, switching the wires on a DC motor will reverse the direction.
Yes, you can visually tell which direction the fan blades were designed to move the air.
Apply power to it, and see if the blades are rotating in the proper direction that they were designed to. If not, you may need to swap the wiring back and mount the fan on the opposite side of the radiator.

quote:

Originally posted by FootbrakeJim:
Looks like a few guys got it right.
Yes, switching the wires on a DC motor will reverse the direction.
Yes, you can visually tell which direction the fan blades were designed to move the air.
Apply power to it, and see if the blades are rotating in the proper direction that they were designed to. If not, you may need to swap the wiring back and mount the fan on the opposite side of the radiator.

Winner winner chicken dinner!

quote:

Originally posted by Lenny5160:
I don't understand some of these blade direction comments. If you reverse the direction of the motor AND turn the blades around, the fan is going to move air in the same direction it did before the changes.

Tony, remember that the whole fan housing is probably being flipped around 180 degrees to mount on the other side of the radiator.

There is a chance the motor is designed with a thrust bearing designed for flow one way.