Electric motor run direction questions and answers:

Frequently-asked questions about the cause of & repair for electric motors that run backwards.

This article series describes A/C electrical motor troubleshooting: here we provide an electric motor diagnostic table, a troubleshooting guide that helps diagnose and repair most electric motor problems for motors found on HVAC equipment in buildings such as air conditioners, furnace or air handler blower fans, oil burner motors, well pumps, and condensate return pumps.

A/C Electric Motor Run Direction FAQs

Questions & answers about the run direction of electric motors & why a motor might run backwards, posted originally

at ELECTRIC MOTOR RUN DIRECTION

Also see ELECTRIC MOTOR DIAGNOSTIC GUIDE

Fatal Shock Hazard Warning: Inspecting electrical components and systems risks death by electrocution as well as serious burns or other injuries to the inspector or to others. Do not attempt these tasks unless you are properly trained and equipped.

Photo: a vintage electric motor from the Master Electric Company, ca 1963.

On 2023-02-26 by InspectApedia Editor - DC motor runs backwards

@Anonymous,

DC motor runs backwards:

I'm unsure of the cause of this DC run direction problem. Almost always when the DC motor runs backwards it's because you've reversed polarity in two of its connections.

Check to see if the brushes have been removed and replaced in the wrong (swapped) position. In particular, when re-assembling the motor, if you mis-align the end plate that determines the exact position of the brushes, that could cause the DC motor to run backwards.

Check to see if motor rotor orienting magnets have been moved from their proper position.

Also, we read that when dis-assembling and re-assembling a DC motor it's possible for the motor to lose its electrical field orientation. A repair procedure described in SOME DC motor guides involves "flashing" the motor's coils by directly applying 12V DC to the motor's field coils (with proper connections of + and -) during re-assembly.

Post a photo of the motor's data tag showing it's brand and model model number and let's both look for the specific IO manual for that motor to get its run direction problem fixed properly.

On 2023-02-25 by Mikee

I have an old 3-phase AC HVAC motor with 160V DC battery back-up capability. The motor has DC four inputs which I assume are brushes and the Field windings. The problem is no matter how the DC side is wired, it turns backwards. (the AC turns correctly) I have tried all wiring combinations on the DC inputs and no luck.

Anyone even hear of an issue like this? I'm mind blown, any help would be appreciated.

A little more info. There are 4 brushes which drop when the AC side fails and then the DC side takes over.

On 2022-06-22 by InspectApedia-911 (mod) - Changing run direction is basically done by moving one wire connection between two points on the motor windings

@Trevor,

TURN IT OFF immediately if you haven't already - to avoid a burn-up

I'm not expert on this but I think the control you were swapping is probably corroded, loose, or defective.

Changing run direction is basically done by moving one wire connection between two points on the motor windings.

IF that switch was loose or corroded it might simply fail to make good electrical contact.

I hope - but don't know - that it couldn't possibly be establishing a connection, albeit a weak one, between both terminals at once - which might certainly fry a motor.

On 2022-06-22 by Trevor

I have a very old one and a half horsepower motor that I bought at a yard sale it is 115 volts or 230 volts and has a ring on the back to change direction I have been running this motor many directions for about a week and one day I tried to switch directions and the motor would not run

so I tried to go back the other direction still would not run so I moved the ring in between directions and got the motor to start but it ran very weak and slow and started burning I am not sure what else to do whether I should put brushes in it or not but I can't figure it out

On 2022-01-11 by Danjoefriedman (mod)

@DARRELL,

Please see the diagnostic and repair suggestions at

at ELECTRIC MOTOR RUN DIRECTION -
https://inspectapedia.com/electric/Electric_Motor_Direction.php

On 2022-01-10 by DARRELL

I have a 1/6 hp (I believe) sump pump motor that has started running in reverse. Sometimes it works right but most of the time its reversed.

On 2021-08-31 by inspectapedia.com.moderator - in single phase motor, when you reverse two leads to change its run direction, you're reversing the polarity of its start winding

@Gary Armitage,

I am not much more certain than you and together it's betting your lathe motor not mine, but as there are no other wires in the photo that could be providing the role of those "BLUE LEADS" I'd assume the two dark leads to terminals 1 and 4 are just what you and the instructions indicated.

As yours is is a single-phase motor, (by your description and because there are only two hot leads to the motor) when you reverse two leads to change its run direction, you're reversing the polarity of its start winding.

So if inspection of wiring or wiring diagram confirm that those two dark leads go to the start winding, (and this is a single phase motor), then you'd be more-certain.


For other readers:

A 3 phase motor would have three hot leads, and by convention if we were going to reverse a 3 phase motor start and run direction we'd probably swap leads 1 & 3.

On 2021-08-31 by Gary Armitage

I have a perfectly good, healthy 1952 English Electric 240v (uk) 1/4HP Single phase, which has been used for many years, with my small modelling lathe. it is wired for CW when viewed from the pulley end. I have never had a reverse on my lathe, but really could do with it.

As part of a complete lathe overhaul/rebuild, I have now got to the stage of working on the Motor. I am now about to renew the perished old mains cable, and have today removed the cover plate. (See photo of terminal housing)

The Note inside the terminal cover states the following:
Quote: "Connect line leads to terminals 1 and 4. To change rotation, interchange blue leads on terminals 1 and 4"

I now plan to fit a new 240v lead, but also to include an additional 1.5mm 4 core lead, and a new 240v DPDT switch, (cross - wired for polarity switching).

The intention is to disconnect the 2 Blue wires from the terminals 1 & 4, and to instead connect them directly to one pair, from the 4 core cable, and up to the switch. The other pair would then return back directly onto terminals 1 and 4.

This should then provide forward and reverse switching. (As long as the motor is fully stopped, prior to switching over !)

My issue is that the so called blue wires are actually jet-black. (See photo) But the only other two are Red. Before I start doing anything, can I assume I am correct that these 2 Black wires are in fact the Blue ones stated in the cover plate (ie - starter coil wires) ? Thanks in advance
Gary

On 2021-04-10 by danjoefriedman (mod)

@Ken,

We figure that the start capacitor is wired to the start winding - Terminal 4. So you've got that figured out;

DId you take a look at any of the motor manuals at our home page on this topic ELECTRIC MOTOR RUN DIRECTION ?

We'd like to find the wire from the other end of the start winding.

On 2021-04-10 by Ken

@danjoefriedman,

This motor has both a start capacitor (Red wire on #4 lug), it also has a run capacitor (blue wire on #5 lug). I conducted a continuity test on all of the wires. I have continuity on all of the wires. So if I am testing wires on any fo the lugs they all have continuity with each other.

On lug one I have the Line1 (Power - black wire) and a black w/ yellow strip wire (BY). BY goes directly to the reset switch. Lug 4 - red wire from start capacitor. Lug 5 - Blue wire from run capacitor, Tan wire to reset switch, and an orange wire that goes to winding. Lug 6 - Yellow wire (to motor), white wire (to motor) Line2 (Power - neutral).

I did a test on all wires by moving them from one lug to the next etc. The motor will revers direction and operate normally if I switch red wire (lug 4) with yellow wire (lug 6) but will only run for 10 secs and then the reset switch is tripped.

Any other configuration results in trip reset switch, blown breaker, motor rotation of about 100 rpms, or no operation. Any other ideas would be much appreciated. Thanks

On 2021-04-04 by danjoefriedman (mod)

@Ken,

Thank you for the follow-up I'm of course very interested as we will both learn something from this. Take a look at the article to which I referred you for more details and options.

On 2021-04-04 by Ken

@danjoefriedman, Thank you, This motor has two external capacitors will start in trying to identify the start winding and work from there. I greatly appreciate your help and will get back with you once this is going.

Ken

On 2021-04-04 by danjoefriedman (mod) - Need to reverse the motor rotation from CCW to CW

@Kenneth, I'm too scared of burning you up to pretend I know the right answer, but we do have both a clue in the wiring notes on the motor label (enlarged below) and in our article on this topic found at

ELECTRIC MOTOR RUN DIRECTION - topic home

where you'll find details of various methods of reversing a motor's run direction

Manually-reversible Electric Motor Run Direction

By swapping wire connections on some electric motors it is possible to change or reverse the motor direction.

Typically purple and yellow wires or wire pairs permit this change. Purple to purple = rotate clockwise

Purple to purple = rotate clockwise
Purple to yellow = rotate counter-clockwise

For an example of electric motor wiring that includes wiring to select electric motor speed options as well as direction of rotation see [live link on the topic page I cited)

Dayton Electric Motor Wiring Diagram [PDF], Dayton Electric Mfg. Co., 5959 W. Howard St., Niles IL 60714 USA, retrieved 2017/07/09, original source: Grainger.com

Your motor doesn't use purple, and wiring differs depending on voltage you're supplying but it's a start.

Other wire change examples to switch electric motor run direction:

Switch Yellow and Blue wires (ending with RED->Yellow & BLUE->Black

Concept: we're reversing polarity at the motor start winding. So if you can identify the start winding that'll be helpful.

If your motor uses a starting capacitor, see which motor winding is wired to the start capacitor - that's the start winding.

When you find the start winding, just swap the two wires that connect to the two ends of the start winding - that should change its direction and thus the rotation direction of the motor at start-up.

On 2021-04-03 by Kenneth

I have an old 2Hp 3450 RPM electric motor that is wired for CCW rotation. Need to reverse the rotation to CW. Unfortunately the name plate is pretty messed up so cant read complete or even if I can reverse the rotation on this motor. It is a single phase 115V with two external capacitors.

I have added the image of the motor with labels as to how it is currently wired. Any help would be greatly appreciated

On 2017-10-14 by (mod) - how to reverse direction of a Master Electric 115V / 230V electric motor

This discussion has moved to its very own page now found

at MASTER ELECTRIC COMPANY MOTORS

On 2017-06-09 by (mod) re: why would a shop fan motor run backwards in higher gear

Loveel

I agree that's a curious question. I but can guess that we've got one of the "motor runs backwards" causes listed in the article above like a bad start capacitor AND perhaps a shorted motor winding that are taken out of the circuit once the motor gets up to speed in the higher gear.

On 2017-06-09 by loveel

What makes a shop fan run in opposite direction in 1st&2nd gear and start smoking, but run in right direction in 3rd gear fine

On 2017-05-0 by Qahtan Al-zaidi

Thank you for the explanation. It is really helpful in diagnosing such a.c motor faults

On 2017-03-19 by (mod) re: motor run direction stamped on a Beckett oil burner motor

Colette

Thanks for the comment, that will help other readers.

Indeed while from the factory we'd expect all of the oil burner components to be correct, at BLOWER FAN ASSEMBLY CLEANING https://inspectapedia.com/aircond/Air-Handler-Blower-Cleaning.php we include an example of how easy it might be for a technician to install a squirrel cage fan backwards with respect to its drive motor shaft - it'll spin fine but it wont' deliver air in that position.

On 2017-03-19 by Colette

@Dan mcallister, yes, you are correct. On my Beckett, it has an arrow indicating a CCW direction. On the covers of both the blower motor and the Beckett, it has a picture of the cage with an arrow going CW from the furnace opening. Hope that helps. And, thank you! Your inquiry helped me! Thank you for your understanding of the units!

On 2016-12-09 by (mod) re: oil burner components & motor run direction must all agree

Dan

On most oil burners the 3 components are hooked up in this order, often from right to left:
Motor

Squirrel Cage fan
Fuel unit

The motor couples to the fan that couples to the drive shaft of the fuel unit (fuel pump in your note)

They all spin in the same direction.

If a motor runs backwards (because of damage or mis-wiring) some components might also rotate but the system won't work at all.

In sum I agree with you. Besides anybody can simply LOOK into the oil burner assembly to see how things have to run.

On 2016-12-08 by Dan mcallister

On a Beckett burner if the fuel pump on the left side turns counter-clockwise and the blower on the right side with the squirrel cage turns doesn't that mean that that blower motor has two turn clockwise to make the oil pump turn counter-clockwise this was a big discussion and I was told I would have to turn counter-clockwise

I don't believe that is correct and the risk of sounding dumb can somebody tell me if I'm right or wrong I believe that if the oil pump is turning counterclockwise the blower motor has to turn clockwise

On 2016-12-05 by (mod) re: why does my motor run backwards after a power outage

Grant,

You might want to review the article above for explanations of common causes of an electric motor running backwards. That's a good place to find things to check and repairs to try.

I suspect you'll find a bad start capacitor

On 2016-12-05 by Grant

I had problems in the summer and replaced a small circuit board in the outside compressor and the unit seem to run fine in the cool mode. After I flipped it to heat mode although I had a little heat I noticed a lot of ice build up on the outside compressor coils.

Then we had a power outage yesterday and I noticed the fan running in reverse when the power came back on? The one thing I cant be sure of was it running in reverse when I changed the circuit board in the summer. suggestions please!

On 2016-11-09 by (mod) re: how to identify electric motor terminals to wire it correctly

Bob,

To identify the specific terminals on your motor and thus the right wiring connections you need just the motor brand (Blaunecht) and model - see your motor's data tag. Then if you don't already have a wiring diagram for the motor I'd contact the company's tech-support:
Whirlpool UK Appliances Ltd
209 Purley Way
Croydon
CR0 4RY
United Kingdom
Tel: 0344 815 8989
Web: http://www.bauknecht.co.uk/

On 2016-11-09 by (mod) re: how can I tell polarity of run and start windings on an electric motor

Aditya:

If your electric motor uses a starting capacitor to operate, you can reverse the starting direction of the motor by reversing the start winding polarity. It should be a simple circuit design to provide either a pair of start buttons or a cycling button that reverses the polarity on the start windings.

To reverse motor direction the motor will, of course, have to stop fully before re-starting in the opposite direction. Matthias Wandel, over at Woodgears.ca has written a nice, clear article on reversing electric motors of various phase and size designs. See https://woodgears.ca/motors/reversing.html

On 2016-11-09 by Bob W.

I have a Bauknecht single phase motor,start and run windings are not fastened to the switch, how can I tell the polarity of the start and run windings before fastening the wires to the switch.

On 2016-10-14 by Aditya mukati

How to turn a motor from left to right with button system

On 2016-08-12 by (mod) re: hydraulic fork lift motor runs backwards after I replaced the brushes

Ron:

It's beyond my expertise so I won't try to say too much, but there are several reasons a motor runs the wrong direction, including the explanations I give in this article

https://inspectapedia.com/electric/Electric_Motor_Direction.php ELECTRIC MOTOR RUN DIRECTION - let me know if that helps you out. You can find that article also (though I've given the link) by searching InspectApedia for "electric motor runs backwards"

On 2016-08-12 by Ron W.

I have an old Clark 24v forklift. Before I got it some one put new brushes in the hydraulic pump motor. NOW THE MOTOR RUNS IN THE REVERSE DIRECTION. I tried swapping the power leads but it still rotates the wrong way. Can you help me? Thank you.

On 2016-05-20 by edward

What is the standard direction of rotation of an electric motor. Also, what is the adequate size of generator to power a 15hp compressor motor.

On 2015-10-12 by Juan Flores Ojeda

Changer left from or to right motor industrial rotation !
Thank you

Question: heat pump ran fine, then started blowing heated air out through the return registers

Turned on our heat pump and system was working fine for about 3 hours. Without warning, the system started blowing heated air through the return. System had been off for about 2 weeks as we transitioned from summer to fall/winter. The filter on the system had just been changed. System is off now. What we thought was smoke was dust from the system. The air handler/return had been replaced about 5 years ago. Again, system seemed to be working fine. Any ideas? - A.S. 11/13/2013

Reply: check for an air handler blower motor running backwards

A competent onsite inspection by an expert usually finds additional clues that would permit a more accurate, complete, and authoritative answer than we can give by email alone. You will find additional depth and detail in articles at our website. That said I offer these comments:

I'm guessing that in shifting from cooling to heating mode, your system correctly reversed refrigerant flow and began using the heat pump to heat building air, OR is running off of back up heat, perhaps electric, depending on outside temperatures. So the delivery of heat does not sound like it's part of the problem about which you ask.

Key in your statement is the rather unusual observation that air started blowing out of the return registers.

I suspect that you have a problem with the blower fan motor, wiring, or controls. It is possible for some electric motors to actually begin to run backwards. While a typical air handler blower fan uses a squirrel cage fan that does not move much air when it spins in the wrong direction, it will move some. And blowing air backwards through the return ducts might indeed be expected to dislodge dust, blowing it back into the occupied space.

Ask for service from your HVAC company, and see if the technician finds a bad electric motor winding, start capacitor, or electronic control, or possibly a control damaged by a power surge or outage.

Reader follow-Up:

We finally got resolution for our system. We had a bad capacitor replaced with the correct size. A few years ago, a capacitor went bad in the air handler and the technician replaced it; the issue (speculation) was that since he did not have the correct size on his truck, he used a smaller size that was minimal at best. It finally wore out. - A.S. 12/4/2013

Reply: Thanks so much ..., I'm glad it's resolved - I had not considered a too-small start capacitor installation as a source of later starting capacitor failure but it makes perfect sense.

...

Continue reading  at ELECTRIC MOTOR RUN DIRECTION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• CAPACITORS for HARD STARTING MOTORS
• ELECTRIC MOTOR DIAGNOSTIC GUIDE - home
• ELECTRIC MOTOR RUN DIRECTION - topic home
• MASTER ELECTRIC COMPANY MOTORS

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ELECTRIC MOTOR RUN DIRECTION FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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