How to Tell If Your AC Fan Motor Is Bad

August 3, 2018

How much do you know about your air conditioner? Would you be able to tell if the fan motor was not working properly?

For those of you who aren’t sure, here’s a crash course from your West Palm Beach air conditioning experts: The fan in your AC unit helps circulate the cool air throughout your home. And while that explanation makes sense, an air conditioner has so many parts, that it can be confusing to figure out which specific component is causing the AC to fail.

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Signs and Symptoms of a Bad AC Fan Motor

The air conditioner fan is located in the condenser unit (the portion of the AC that is parked outside your home). Therefore, to determine whether or not this part is working, you’ll have to walk outside and look at the fan through the vents of the condenser unit.

Signs that your fan is having issues include the following:

The fan won’t start even though the AC is on
The fan won’t stop, even when you shut the AC off
The fan turns on, yet the blades are rotating very slowly
There’s a rattling noise coming from the condenser unit when the fan is turned on

That being said, it could be tricky to figure out whether the issue is the fan or the capacitor since the capacitor is the part that provides the energy for the fan motor to operate.

One way to know for sure is to unscrew the side panel of the condenser unit (make sure you turn off the power breaker that provides electricity to your air conditioner before you do this). The capacitor looks like a large, cylindrical battery, with cables connected to it. Its top should be flat. If it looks swollen, the issue is with the capacitor. If it’s flat, you could narrow down the malfunction to the fan.

Fixing this issue as soon as possible is crucial, since having a faulty fan can shorten the lifespan of your AC compressor, resulting in the need to replace both parts. Purchasing a new compressor is substantially more expensive than replacing the fan.

How to Check if Your AC Fan Motor is Bad in 7 Steps

When the fan is not working properly, you won’t feel air coming out of your vents, and the air conditioner coils will end up freezing over. Therefore, it’s essential to keep it in good condition if you want your air conditioner to work.

Follow these simple steps to test your air conditioner’s fan motor:

Step 1. Ensure the Thermostat is On

Is the thermostat on? Make sure the thermostat is turned on. Don’t laugh. It’s one of the main culprits that makes people think their AC is not working.

Step 2. Check for Tripped Breakers

Is there a tripped breaker? Locate the circuit breaker panel and check if there’s a tripped breaker. Each breaker switch has three settings: “On”, “Off”, and a neutral setting. If the breaker that’s labeled “air conditioner” is in the “off” setting, set it to the middle neutral position before turning it back to “On”.

Step 3. Replace Air Filters

Are the air filters clean? Check the air filters to see if they’re clean. If they’re caked with dirt and debris, replace them. Clogged air filters will block the airflow, causing a chain reaction. If they’re clean, it’s time to move on to step four.

Step 4. Examine Outside Fan

Is the fan spinning? Walk outside to check the condenser unit (the big box that sits outside your home). You’ll be able to see the fan from the top. If the air conditioner is on, you should be able to hear the compressor (the loud humming sound that’s typical of a running air conditioner) and you should be able to see the fan blades turning. If the AC is on and the blades are static, you know there’s an issue.

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Step 5. Clear Fan Blades of Obstructions

Are the fan blades obstructed? Go back inside and turn off the air conditioner. Then walk back outside and insert a screwdriver or similar tool into the slits on top of the condenser unit and try to move the fan blades with your tool. This is to check if they’re spinning freely or if maybe there’s a fallen branch or something else that may be restricting movement.

Step 6. Try Kickstarting Fan Blades

Will the blades move on their own if you kick start them? If they move freely, go back inside, turn the AC back on, and use your tool again to kick start the fan blades. If they start working once you start them manually, then the blades are working fine and the problem is the capacitor (which is the AC part that makes the fan run).

Step 7. Inspect the AC Capacitor

Inspect the AC capacitor. You’ll need a capacitor tester for this (available at any hardware store). Turn off the power source to your air conditioner.

For a troubleshooting guide, check out our blog: How to Tell If Your AC Capacitor is Bad

How to Test Your AC Fan Motor

To test the fan motor on your air conditioner, you’ll have to do a continuity test. Click here for a video tutorial. Before you start, make sure the thermostat is set to cool and that the temperature setting is as low as it will go.

Step 1. Check the power

If you suspect the fan motor is bad, the first thing you should check is the power to the motor and the power to the air conditioning unit. Locate the circuit breaker and ensure it hasn’t tripped. If the power is fine, check to see if there is proper voltage. You can do this at the transformer, checking for a fuse in the low-voltage circuit.

Step 2. Check the windings

Next, check the windings of the fan motor for an open or a short. To do this, you’ll have to measure the ohms. If your fan motor is a 120V, it will most likely have four colored wires (black, blue, red, yellow, etc.), as well as a white wire, a black wire, and two brown wires. If you’re working with the wires, do a resistance check between the white wire and each of the colored wires. The higher the resistance is, the lower the speed is, with each colored wire representing a different speed.

Look for a resistance reading. A reading of zero means the fan motor winding is likely shorted and causing the breaker to trip or blow. An infinite reading, on the other hand, may indicate an open motor winding. If either of these conditions exists, the fan motor needs to be replaced.

Step 3. Inspect the capacitor

Keep in mind that just because the fan motor isn’t running, doesn’t mean it’s bad. If the power supply is fine and the windings are in good shape, check the capacitor next.

The capacitor helps the fan motor run. Delivering torque to the fan motor, if the capacitor is faulty, there won’t be enough power delivered and the blower wheel, fan belt, and other important components can cease to operate.

To inspect the capacitor, make sure it is discharged. Once it is discharged, use a capacitor tester to check the microfarad reading. The reading should be within 10 percent of the rated capacitance on the capacitor. If the reading doesn’t match the rating, replace the capacitor.

AC Fan Motor Maintenance

The fan motor is one of the most important components of your air conditioning system. Often referred to as the “heart” of HVAC equipment, fan motors work hard and under tough conditions for years. While fan motors don’t need much, overlooking maintenance can have a serious impact on your air conditioning system and the comfort of your home.

Sometimes, replacing the fan motor in your air conditioning system is inevitable, but with routine maintenance, you can prolong the lifespan of your air conditioner. When it comes to fan motor burnout, dirt is the biggest culprit. That’s why the best thing you can do is to keep everything clean. When dirt builds up in the fan motor, it can block the motor hole and cause the component to overheat. Fortunately, scheduling routine maintenance check ups with your trusted HVAC technicians will ensure your fan motor is clean and in good overall shape.

AC Repair in West Palm Beach & South Florida

At Sansone Air Conditioning, we provide a full range of AC services for your home or business, including air conditioning repair. If you live in Broward, Palm Beach, or St. Lucie, let us help you make sure your air conditioner is running as efficiently as possible.

If you suspect your AC fan motor is bad and needs to be replaced, or if you’re unsure what’s causing your system to falter, the team at Sansone is here to help. We’ve been in business for more than four decades and pride ourselves on providing West Palm Beach area residents with the best in HVAC services and customer care. Contact us today to learn more about our quick, efficient and economical AC repairs services or schedule an appointment online below.