3 Signs of A Bad HVAC Motor and How To Test It

How Do I Test My AC Blower Motor?

When it comes to your AC, there are many things that, at first, you won’t be able to understand.

The first thing that comes to mind is the blower motor, it is one of the most important parts of your HVAC systems, and it helps your AC unit to circulate the cool air throughout your indoor living spaces.

While its definition is pretty straightforward, an HVAC system has so many parts, and it can get overwhelming and confusing to some people when it starts to fail.

How do I test my AC blower motor? When it comes to testing your AC blower motor, the first thing to do is to check the power, then you check the winding, and last but not least, to inspect your capacitor.

This article will allow you to learn more about the HVAC blower motor and what it does in your overall system. Besides that, it is important to understand how to test and troubleshoot it, so you know when to call in your HVAC technician.

The Definition Of An AC Blower Motor

The HVAC blower motor is the cooling and heating system components that are mainly responsible for sending conditioned air from your air conditioner, heat pump, or your furnace into your living spaces.

Once your system starts to heat or cool the air, your blower motor will force it through the duct system and out of the vents in your rooms or throughout the house.

A blower motor is known to be the main component within your home’s HVAC system. There are two types of blower motors – the single-speed motors and the variable-speed motors.

Single-speed motors are known to blow air at one constant speed, while on the other hand, the variable-speed motor can adjust its speed to blow air at different levels.

How A Blower Motor Works

As you know, your thermostats work within your home heating and cooling system, and they monitor the temperature. When the temperature begins to drop below the thermostat setting, it will signal the furnace to work.

The furnace will then create hot or cold air, which then needs to circulate in different parts of your house. This is when the blower motor will start to do its job.

The blower motor is responsible for taking the cooled or heated air within the furnace and circulating it in your indoor living area. It normally does it by spinning a fan, which then blows the air through the ventilation system. Even a tiny blower motor can make a difference, moving a large volume of air.

Symptoms And Signs of A Faulty Blower Motor

When it comes to finding the signs and any symptoms of a bad blower motor, keeping it clean is the major step. But just beware that even a well-maintained motor might stop at any given time, and then it is time to check for an open or a short.

Fan motors are considered to be the unsung heroes of HVAC equipment. This is because they work unobtrusively and silently for many years, even under very tough conditions.

They might not need a lot of love, but you need to pay attention to them for their periodic maintenance.

Here are a few symptoms and signs that you should keep an eye on to know if your AC motor is bad or not.

The Fan Won’t Start

This is one of the most common symptoms to look out for to find out if your AC fan motor is misbehaving. When your fan does not start even though the AC is already turned on, this can be a great indication that there is a fault in your motor.

If the AC is running without the fan circulating all the air surrounding it, it can lead to evaporator coils freezing over. Once this happens, your HVAC unit is at risk of suffering more serious damage.

The Fan Continues To Run

The opposite of the first one can also occur, for instance, if your fan continues to run even though you switch off the air conditioner.

In some rare cases, this is caused by a malfunctioned thermostat, and replacing it will have it up and running again.

If the thermostat is not the case here, the most likely problem is the stuck relay switch inside your HVAC unit. Relays are responsible for opening and closing an electrical circuit in an air conditioner.

As a result of this faulty behavior, the electric power to the fan motor does not stop, and the fan eventually keeps running.

The Fan Rotates Very Slowly

Another sign that you should be looking out for is the rotation of the fan. It can get pretty annoying if you found out that the fan is working, but it rotates very slowly. As a result, it can only generate weak airflow.

If your AC tends to have different fan settings, check if it is properly configured at their right speed. If that is not the case, it could mean that your motor bearings need some lubricant or the capacitor is failing.

Rattling Or Buzzing Noises

When it comes to noises, it is always not a good thing if you hear them, especially if it comes from the inside of your unit.

If you hear some loud rattling noise, some minor issues like small stones or debris are caught in your condensing unit. A rattling noise can also be caused by some loose or unbalanced fan blades striking from any side of your housing unit.

If you don’t happen to see anything stuck in your unit and the fan blades turn freely and smoothly, it is more likely to be caused by some fan motor issues. A buzzing sound is another sign that the blower motor is reaching its end of life.

Testing Your AC Fan Motor

When it comes to testing your AC fan motor, you need to be familiar with some continuity tests. This way, you are making sure that it is safe and in good condition but before you start, make sure that the thermostat is set to cool and that the temperature setting is as low as it can get.

Check The Power

If you suspect your fan motor is bad, the first thing you should probably check is your motor’s power and the power of our overall air conditioning unit. If you find that this is at fault, find the circuit breaker and ensure that it is not tripped.

If the power turns out to be okay, check to see if there is enough proper voltage. You can actually do this at the transformer and check for a fuse in the low-voltage circuit.

Check the Windings

The next step in your test is to check the fan motor’s windings for an open or a short. To be able to do this, you might need to measure the proper ohms.

If you have a fan motor that is 120V, it will most likely have at least four colored wires. It consists mainly of black, blue, red, yellow, white, black, and two brown wires.

If you are new to working wires, you need first to do some resistance check between the white wire and each of the colored wires. The higher the resistance is, the lower the speed will be, and each colored wire represents a different kind of speed.

You just need to be familiar with some resistance reading. A reading of zero means that the fan motor winding is likely shorted and causing your breaker to trip or blow.

On the other hand, an infinite reading means that it can be an open motor winding. If either of these conditions exists, the blower motor needs to be replaced.

Inspect The Capacitor

You have to bear in mind that if the fan motor is not responding or running, it does not mean that it is faulty or bad. If the power supply is good and the windings are actually in good condition, you should check the capacitor next.

The capacitor helps the motor to run smoothly, and if the capacitor is at fault, there won’t be enough power to be able to deliver, and the other important components will cease to operate.

To fully inspect the capacitor, make sure it is discharged properly. Once it is discharged, use a capacitor tester to check its microfarad reading.

This type of reading should be within 10 percent of the rated capacitance on the capacitor. If the reading won’t match with the proper rating, it is time to replace the capacitor.

Ways To Check The Quality Of Your AC Fan Motor

When your fan is not behaving properly, you will not get enough air coming out of your vents. As a result, the air conditioner coils will freeze over, and therefore, it is very important to keep it in good condition if you want your AC to work properly. Here are some ways to check the quality of your AC fan motor.

Ensure The Thermostat Is On

The first thing that you need to do is to check if the thermostat is properly on. It might be the most obvious thing, but a lot of people found out that sometimes it is the thermostat’s fault. It is one of the main culprits that make people think their AC is not working properly.

Check For Tripped Breakers

Locate your circuit breaker and check if there is a possibility of a tripped breaker. Just remember that a breaker switch has three different settings: On, Off, and the neutral setting.

If your air conditioner’s breaker is in the offsetting, set it to a middle neutral position before turning it back on.

Replace Air Filters

The next thing to check is your air filters. Make sure to check it every now and then to see if it’s full of dirt or any kind of debris.

Check if it is clean or if they are caked with dirt, make sure to replace them as soon as you saw them. Clogged air filters will only block the airflow, and it can cause a chain reaction.

Check The Outside Fan

Check your condenser unit outside. It is the big box that sits outside your house. You will be able to see a fan from the top, and if the air conditioner is on, you should be able to hear the compressor with a loud humming sound that is typical of the usual air conditioner.

If you see that the fan blades are kind of static, you should know that there is an issue.

Clear Fan Blades Of Obstructions

Check if the fan blades are obstructed and if yes, then go back inside and turn off the air conditioner. Continue to walk back outside and try to insert a screwdriver or a similar tool into the splits on top of the condenser unit.

Try to move the fan blades using this tool, and with this technique, you will be able to check if they are spinning freely or a fallen branch prevents them from doing their regular movement.

Try Kickstarting Fan Blades

Examine the blades if they move on their own if you kick start them. If they happen to move freely, go back inside your house and then turn the AC back on.

Using your tool again will be able to help you kickstart the fan blades. If they start working once you are able to start them manually, then the blades are working as designed. The problem is the capacitor, which is the AC part that makes the fan move.

Inspect The AC Capacitor

Last but certainly not least is always to inspect the AC capacitor. You might need to have a capacitor testing for this one, which can be available in any hardware store. Make sure to turn off the power source to your air conditioner before proceeding with the test.

Prolonging The Life Of Your AC’s Fan Motor

As mentioned above, your fan motor is the hardest working part of your HVAC system, and it will wear and tear eventually through time.

However, there are still ways to prevent it from burning out sooner than the intended lifespan with proper HVAC maintenance.

One common reason why your AC fan motor deteriorates is that it has a lot of dirt building up around the fan motor.

These specks of dirt can creep into any holes of the motor, and it can cause friction for the inner workings, which can stress the motor, causing it to overheat.

Make sure to perform some regular dusting in and around your motor hole so that you won’t have to deal with this issue.

This easy maintenance routine will help you big time prolong your blower motor’s lifespan and prevent other serious damage to your AC.

If it happens to be that you are not the most diligent person when it comes to AC maintenance, then the best way is to ensure you have a maintenance plan sign up.

This maintenance plan comes from your HVAC company provider, and they will help you with all your needs when it comes to maintenance. Most maintenance happens during biannual HVAC tune-ups and as a part of a routine maintenance visit.

The skilled professional you will ask will be able to inspect the unit, clear away some of the dirt, check the fan, and clean the fan motor if necessary.

Blower Motor Maintenance

Having proper maintenance will help you ensure that your family will be able to enjoy your home all year round.

Always make sure that you should always check your fan blades before the heating season, check your motor belt for wear and tear, and make sure that the motor and bearings are properly lubricated.

Just bear in mind that still issues can arise to your blower motor with proper maintenance. Some common issues involve the resistor, some fan relay, and the climate control switches.

You should not be worried about it as an HVAC professional will be able to evaluate it and fix your common issues right away.

Blower motor failure can also be derived from bearing wearing out, the motor wearing out, and the obstructed fan cage. Proper maintenance, like regular tune-up or cleaning, will be able to prevent the motor from becoming dirty.

A furnace that resides in basements and laundry usually has a lot more dirt in them, so small lint particles will often make their way into the motor.


Overall, figuring out how your HVAC system works internally is one of your main weapons in fighting off these bad scenarios. If you have a better understanding of how it works, you will be able to troubleshoot it the right way.

Always follow your maintenance routine as it can prevent all the scenarios mentioned above. If you are unsure of what to do and DIY is not your cup of tea, then call your local HVAC technician to help you figure out the issue.

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