Condenser Fan Motor Runs Backward? (Here's What You Can Do)
Most motors are designed to run only one way, clockwise or counterclockwise. They are not made to run both ways unless it is a multidirectional motor. Any kind of motor that runs the opposite way than what is intended will not produce the effects they are supposed to. In other words, your AC will not blow cold air.
If your condenser fan motor is running backward, there is something wrong. Either the wires are crossed, the motor is failing, or the start capacitor is going out. But since there are several types of motors, you have to know what you are working with first.
Clockwise or Counterclockwise
A manually reversible electric motor can be reversed or changed by switching two wires. There will typically be a yellow and purple wire in the motor that can be reversed by switching them up. Yellow to yellow rotates clockwise while yellow to purple runs counterclockwise.
If you read the electric motor data tag on your condenser motor, you should see a set of letters telling you which way the motor should go. CW for clockwise and CCW for counterclockwise.
Interesting Tip: You can find a lot of information on the electric motor tag including the rotating speed, model number, the size of the motor, and the amperage.
Basic Parts of an Electric HVAC Motor
First, let’s go over the basic parts of an electric air conditioning motor. It helps to know what parts of the motor may be causing the problem. There are four main parts of the electric HVAC motor.
|Part||What it Does|
|Electric motor start switch||Connects the electrical power to the motor to wind the stator until it has reached 75 to 80% of its run speed|
|Electric motor windings||· Start winding is what starts the motor running from a stopped position|
· Run winding is what keeps the motor spinning
|Electric motor stator||A core that houses the start and run windings around it to create a magnetic field|
|Electric motor rotor||Follows the magnetic field to spin the motor shaft|
The Most Common Cause of a Reversed Motor Fan
According to the experts, the most common reason for your condenser motor fan running backward is if wires are crossed. If you have had someone replace the motor or do any other kind of work on your AC lately, call them back to fix it for free. If not, you can fix it yourself pretty easily.
Changing the Direction of the Motor
To change the direction of the condenser motor you have to alter the magnetic field. To do that, just switch the main and starter wires. This switches the polarity of the magnetic field and reverses the motor.
The problem is that some motors have different color wires. In some, you will find that these wires are blue and yellow while others are purple and yellow. Fortunately, there is usually a diagram showing which color wires are supposed to go where. If not, you may want to Google the motor by its model number before doing anything else.
If the Motor is Failing
If it is not the wiring, you probably need a new condenser fan motor. This is not difficult to fix, but you need to have the correct part for your AC unit. Let’s look at the steps in changing a condenser fan motor.
Changing the Condenser Fan Motor
While you are at it, you should also change the start and run capacitor. Some have these two combined in one while others have both separate. Either way, change them both while you are changing the motor.
Step One: Be Sure You Have the Right Parts
The most important thing to do first is to make sure you have the correct motor. To do this, you need to know these things:
- Horsepower (HP)
- Shaft size
- Rotation per minute (RPM)
- Mounting style
- The direction of the fan
All of these must match the motor you are replacing. The condenser fan motor capacitor should also be checked. The capacitor must match the motor. Although the voltage can be higher, the microfarads (MFDs) should be the same. And note whether your unit has a dual or individual capacitor.
Step Two: Turn Off the Electricity
You should always turn off the electricity to whatever you are working on. And check it with a voltage meter to be sure it is off before touching anything.
Step Three: Remove the Panel
Take off the panel on the side of the condenser to get to the condenser motor. This is usually an easy thing to do by just removing a few bolts or screws.
Step Four: Take Pictures
Always take photos or write down which wires go to what. That is one thing you have to know when you are putting things back together. That is the most common cause of fan motor reversal. Also make sure you get a shot of the fan, so you replace it the correct way.
Step Five: Remove the Fan
Unscrew the cage over the fan and turn it over to expose the fan. Remove the set screw-off the hub of the fan. Use a hub puller or channel locks to remove the hub.
Step Six: Remove the Motor
Remove the four nuts holding the motor on the fan. Check the HP, amperage draw, and the RPMs to make sure you have the correct motor. Take the motor off and replace it with the new motor.
Step Seven: Putting the Fan Back On
Put the fan back on, making sure it is the correct depth from the motor and pointing in the right direction. Connect the wires together the way they were before you removed the old one.
Step Eight: Changing the Capacitor
This is easy since all you have to do is disconnect two wires (usually brown) from the old one and attach the two wires to the new one.
Step Nine: Check the Rotation
Go ahead and turn the electricity on and check that the fan is blowing in the right direction before putting everything back together. But be sure to turn the power back off before continuing.
Step Ten: Putting it Back Together
After you turn the power back off, replace everything the way it was. Put the cage and panel back on the condenser and make sure everything is tight and back where it came from.
Turn the power back on and make sure everything works. Be sure that nothing is rubbing or hitting. Also, make sure nothing is vibrating or wobbling. This could mean that something is loose.
What if I Cannot Get the Fan Blade Off?
Sometimes removing the fan blade from the hub is difficult. After years of running, it can be stuck or it may be rusted or corroded. If you cannot get it off with a hub puller or channel locks, there are some other tips that may help.
- Try spraying some WD40 on the lock nut and shaft
- Use a sand cloth to remove any rust or corrosion
- Hit the blade hub with a hammer a few times
- Use a torch to apply some heat
- Try a hack saw and deep well socket
There are several reasons why a motor does not start. Some are more obvious than others. Here are the most common reasons:
- The reset button needs to be pressed (not all AC motors have these)
- Fuse or circuit breaker may be tripped
- Check voltage with a voltage meter
- Make sure all switches are turned on
- Check that all wires are connected tightly
- The motor may be shorted out or jammed
If all else fails, call an HVAC professional.
I am a DIYer who loves writing about anything home-related. When I am not writing, you can find me studying for my PhD in Psychology, photographing nature, and swimming at the lake with my grandkids.
More by Patricia Oelze