How to Service a Fan Motor

How to Service a Fan Motor

The fan motor is a vital part of the intricate machinery that makes up your HVAC system. Its most important function is to facilitate the dissipation of heat, an essential process for cooling your home or business.

Often, problems with fan motors occur when they aren’t properly maintained. Follow these tips to keep your fan motor running smoothly:

Choosing the Right Fan

The fan motor is the part of your air conditioner that pumps out the cool air, so it is important to keep this component working well. Problems with the fan can lead to overheating, which can wreck havoc on your entire system.

There are several factors to consider when choosing a fan for your particular application. Whether the fan will be used to clean or transport materials, how much air the fan is expected to move per hour and what the ambient conditions are like will all impact fan choice.

Another thing to consider is if the fan blades are balanced properly. If not, they can cause vibrations that will ruin the bearings in the fan motor and eventually make it stop working.

If you’re not sure, look at the side of the fan for a small arrow. The arrow should be on the intake side, and it’s usually easier to see on glass or metal side panels.

It’s also important to remember that all fan efficiency ratings are given under standard air conditions. That means the actual Air conditioner efficiency that you’ll get will vary based on the temperature and humidity of your location. This can have an effect on the total energy cost of the fan and should be taken into consideration.


While replacing a fan motor is a standard procedure for servicing split systems, it does require attention to detail. Using the right parts and following best practices can help ensure the new motor is installed properly.

A motor’s failure can be caused by a number of things. Electrical problems may prevent the motor from turning on, or it might fail due to mechanical wear and tear. The bearings might also stop working if they’re not lubricated properly. In any case, it’s important to troubleshoot the problem before replacing the motor.

A good way to test a fan motor is to use a multimeter. First, set the multimeter to the ohms setting. Then, touch one probe to each of the terminals on the motor. If the reading is infinite, the motor is bad and needs to be replaced. If the reading is zero, then the motor is in good condition and does not need to be replaced.


There are a number of reasons why a fan may not be operating properly. The problem may be as simple as replacing an electrical cord, cleaning or servicing the switch, lubricating the blades, or as complex as re-soldering wires that have broken off inside the motor casing. If the fan doesn’t run at all, check that the circuit breaker has not been tripped or a fuse blown in the disconnect box. Check for a short by doing an ohms reading on the white and other colored wires in the motor. An ohms reading of zero indicates that there is a winding open; an infinite reading means that the motor winding is bad and needs to be replaced. If a multispeed fan quits working on one speed, clean and service the clutch knob and gear assembly.

If there is line voltage (24V) being fed to the motor but it still doesn’t turn on, then a bad capacitor could be the problem. Disconnect the motor and use a designated capacitor tester to check the microfarad reading; if it doesn’t match the rating capacity then the capacitor needs to be replaced. Be sure to replace it with a capacitor of the same uf and voltage ratings. Preventive maintenance, such as lubricating the motor and keeping it clean, will reduce downtime and help to extend the life of your fan.


If the fan motor isn’t working or is making strange sounds, there are some basic repair techniques that can be employed. First shut off the power to the fan at the circuit breaker or fuse box. If you don’t, the breaker or fuse could become damaged from the high current flow through the motor.

Once the fan is turned off, examine it for damage, like bent or cut blades. Usually, these can be straightened by hand. It’s also a good idea to check the gear assembly and clutch knob for alignment and wear, especially if the fan is an oscillating model. Tape small washers on the top side of each fan blade to test the balance. If the blades are out of balance, they can be corrected by moving the washers around on the top of the blade until a proper balance is achieved.

When the fan keeps tripping the thermal overload switch, it’s likely due to a short in the motor windings. A professional technician can perform a simple resistance check to see if the windings are open or closed Air conditioner manufacturer by measuring the ohms on the capacitor with a multimeter.

If the capacitor is not bad, then the problem is probably with the wires or switch, which can be replaced by a professional. To reinstall the fan, first reconnect the wiring and remove the capacitor. After that, the motor can be mounted. Be sure to use the correct balancing washers, as well as re-solder the wires and replace the connector on the control unit. Also, if the old motor came with insulation, replace it. The extreme under-dash temperatures can dry it out in a few months.

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