AC Fan Motor Cleaning, Maintenance, and Oiling

Before performing the cleaning and maintenance procedure(s) on the AC motor, ensure power to the AC has been shut-off. The Service Disconnect must be removed before beginning any type of work on the AC unit.

Step 1: Cutting Power to the AC Unit

This is accomplished by removing the disconnect at the Service Disconnect Box. The box is located in close proximity to the AC, and will be mounted onto a wall, pole, or frame within three (3) feet of the AC unit. The box can be found by following the large, cylindrical cable running from the unit. Photo #1 shows an opened Service Disconnect box with the disconnect pointed out.

A lever located on the bottom of the box activates the spring-loaded latch that holds the front-cover of the box closed. Using your finger, push the lever backwards. Note that activating the lever causes the portion of the latch that protrudes through the cover to retract. Using your free hand, slide the Service Disconnect Box cover downward, and then swing it open.

Once opened, grasp the ring and pull it toward you to remove it. With the disconnect removed, there is no power going to the AC, and it is now safe to work on.

Step 2: Checking the Motor for Oil Ports

Check the motor’s frame for oil ports because a motor that has oil ports can be maintained without removing it from the AC. Photo #2 shows an oil port that is closed off. If it had been a usable oil port, there would be a removable plastic cap that when removed, exposes a small hole in which oil would be added.

If the motor has oil ports, position the motor so the ports are pointing upwards. It is necessary for the ports to be in this position or the oil will not flow into the bushing.

• Using your fingernail, pull the plastic cap off to expose the oil port opening.

• Using an oiler with an extended spout, slowly drip oil into the oil port opening. Because the oil is slow to drain, pause after each drop. When the oil port opening is once again clear, add the next drop of oil.

• Once completed, wipe any excess oil from the case, and ensure the oil cap is securely positioned back into the oil port(s).

Oil Maintenance Schedule

1. Regular, Annual Maintenance for a free-spinning motor is 2 to 3 drops per oil port.

2. 1st time Maintenance for a tight-spinning motor is 5 to 6 drops per oil port.

Sometime the front and rear oil ports will not be aiming upward at the same time. In this instance, perform the oil maintenance on one port at a time. Before repositioning the motor to access the other port, be sure to replace the oil cap on the first port to prevent oil from draining out.

If this is a 1st time oil maintenance, be sure to spin the fan motor shaft frequently in order to draw the lubricating oil onto the motor’s shaft. Spin the shaft in both clockwise and counterclockwise directions after each drop of oil. Once the motor’s shaft starts spinning freely again, then the procedure has been completed.

In the event the motor’s shaft spinning does not improve with oil maintenance, then the motor will have to be cleaned, and lubricated from the inside.

Note: Motors not equipped with oil ports or motors that require cleaning should follow the remaining steps to clean, maintain, and oil the motor.

Step 3: Marking Wire and Fan-Blade Positions

Before removing the fan-blade from the motor’s shaft, use a permanent marker to mark the shaft where the fan-blade lock-down is positioned (see photos #3 & 4). This will allow you to position the fan-blade back into its correct location. If the fan-blade is not returned to its correct location, it could rub against the AC frame, and/or not provide maximum air movement.

Prior to removing the motor from the AC, mark the position of each of the wires. The wires can be marked by placing a piece of masking tape around the wire, and writing on the tape. If masking tape is not handy, then a simple drawing of the wire locations can be made; however, do not forget to record the wire color for each connection location.

Step 4: Disassembling the Motor

Before removing the nuts/bolts that hold the motor case together, make a mark on the outside of the case so the motor can be reassembled with the correct case orientation (see photo #5).

This step becomes very important if the motor case splits in two (2) halves. These types of motors have the stator (fixed winding) split between both halves. If the halves are not oriented correctly, the motor will not work. However, most modern AC motors will have a case that contains the full set of windings, and covers that are mounted on each end. Regardless, it is always a good practice to mark the case section to ensure the orientation will always be correct.

After marking the case and removing the bolts/nuts that hold the top cover (cover closest to where the fan-blade was mounted) onto the motor’s case, slowly slide the top-cover off the motor’s shaft. Photo #6 shows the inside of the motor with the top-cover removed. At this point, the armature can now be removed for cleaning (see photo #7).

Step 5: Cleaning and Oiling the Motor

Using a clean, soft cloth, wipe away the collected surface dirt and oil from both the front and rear armature shafts. Utilizing a piece of extra-fine steel wood, polish the shaft lengthwise until blemishes and rough areas are removed (see photo #8).

Be careful not to clean away the mark on the motor’s shaft that indicates the fan-blade positioning. Next, check the windings mounted to the inside of the motor’s case for dust and debris. If present, then use a vacuum cleaner or some canned air to remove the collected debris from the windings.

To clean the front-cover bushing, twist a soft clean cloth through the bushing opening (see photo #9), repeating until the inside of the bushing is clean and shiny.

The rear bushing (photo #10), will probably not need to be cleaned; however, if the inside of the bushing does not look clean and shiny, then it will need to be cleaned. A clean cloth wrapped around a wooden dowel or your finger will be used to clean the inside of the rear bushing. Simply insert the towel covered dowel into the bushing and twist. Periodically remove the dowel and re-wrap it in a clean section of towel. Continue this procedure until the inside of the bushing is clean and shiny.

Once the bushing(s) have been cleaned, it’s time to lubricate them. As you can see from photo #11, there is an absorbent material, which is used to hold oil, surrounding the bushing. As the motor’s shaft spins, oil is drawn from the material through the porous bushing to lubricate the spinning shaft.

Drip oil onto the absorbent material, one drop at a time, applying it evenly around the material’s surface (see photo #12). However, do not use more than ten (10) drops. Move on to the other bushing while the oil soaks into the material surrounding the first bushing.

After oiling the second bushing, re-check the first one, and take note of any puddling or any heavily saturated looking areas. If you find either of these, then use a towel to blot up the excess oil. If the material still looks dried out, then another 4 to 5 drops can be added to each bushing.

Step 6: Re-Assembly

Once the cleaning and oiling have been completed, put the armature back into the motor, short-shaft first. Replace the top-cover, ensuring that the case marks are lined up. Replace the motor’s bolts/nuts, but do not fully tighten them. Spin the motor’s shaft to ensure it is spinning freely. At this point, the nuts can be fully tightened. Give the shaft another spin to ensure it is still free-spinning.

The maintenance has now been completed, and the motor can be put back into the AC. Using your hand drawn diagram, or masking tape wire markers, wire the motor back into the AC. Slide the fan-blade back onto the motor’s shaft until the fan-blade position indicating mark has been reached. Tighten the fan-blade lock-down, and give the blade a spin. It should spin effortlessly, and continue spinning for a few seconds.

Maintaining you’re own equipment can save considerable amounts of money over the long haul. It is not difficult, and if you do not mind getting your hands dirty and spending a bit of time working, you can keep your equipment in good operating condition for longer than you might think.

Using this article and the Bathroom Exhaust Fan Repair and Maintenance Guide article, you can clean and oil almost any small electric motor found around the home. These procedures will work for any type of fan, AC, or refrigerator motor.