Author: Prof. Rodrick Rippin Jr. | Last update: Wednesday, September 17, 2025
How to Test AC Fan Motor with a Multimeter
Turn off the power to the AC unit before testing the motor.
Ensure the multimeter is in the ohm setting. ...
An infinite multimeter reading indicates an open circuit, meaning your motor is faulty.
A zero reading signifies a short circuit and the fan motor is faulty.
How to check if a fan motor is bad?
7 Signs Your AC Fan Motor Is Failing
The Fan Won't Come On. A sure sign of a bad fan motor is a cooling fan that will not come on. ...
The Fan Blades Rotate Slowly. ...
The Condensor Makes a Rattling Noise. ...
The Fan Runs Intermittently. ...
Fan Runs When Unit Is Off. ...
You Smell Burning Smells. ...
Frequently Tripped Breakers.
How to test a motor to see if it is bad?
How To Check If an Electric Motor Is Going Bad
Check the Bearings and Shaft. A motor's bearings are one of the most common components to go bad. ...
Inspect the Motor Windings With a Multimeter. ...
Test the Power With a Multimeter. ...
Ensure the Fan Is in Good Shape and Secure.
How do you know if your fan motor is burnt out?
Some commonly occurring signs that you have a problem with your blower fan are that there is no air coming out of the registers even though the system is running, there is a loud rattling noise, and there is a burning-type smell within the system.
How do you test a cooling fan motor?
Testing the radiator fan motor is as simple as connecting two jumper wires to its pigtail harness – one from the positive battery terminal and one from the negative. When it's connected, the fan should immediately turn on and spin at full speed, smoothly, and without any abnormal noises.
How to test an electric motor.
How do you test a fan motor with a multimeter?
How to Test AC Fan Motor with a Multimeter
Turn off the power to the AC unit before testing the motor.
Ensure the multimeter is in the ohm setting. ...
An infinite multimeter reading indicates an open circuit, meaning your motor is faulty.
A zero reading signifies a short circuit and the fan motor is faulty.
What are the symptoms of a bad cooling fan relay?
For The Car Owner
The engine runs hot or overheats. ...
The cooling fans don't work. ...
The cooling fans keep running. ...
Warning lights. ...
Poor air conditioning performance. ...
Swapping Relays. ...
Measuring the Relay Coil's Resistance. ...
Listening for Noises.
How do I know if a motor is burnt out?
6 Signs of Electric Motor Failure
Overheating. Is your motor consistently overheating? ...
Vibration and Unusual Noises. ...
Frequent Tripping of Circuit Breakers. ...
Decreased Performance and Efficiency. ...
Excessive Energy Consumption. ...
Irregular Motor Operation. ...
Operating Conditions. ...
Vibration Analysis.
What is the life expectancy of a fan motor?
A blower motor should last at least 10 years, and could last up to 20, depending on the type of HVAC unit you have in your home. There are a few warning signs that your blower motor is damaged, including little-to-no airflow coming from your vents, a burning smell, and skyrocketing energy bills.
What is the first thing to check if the electric fan is not functioning?
When your electric fan does not seem to work like it used to, the first thing you should do when troubleshooting is to make sure that the power supply to our power outlet works well. Turn your fan on to see if the motor works.
How do you tell if a motor is worn out?
Description
Excessive Smoke. Visible smoke coming out from the exhaust in unusual amounts.
Strange Noises. Unusual sounds like knocking, popping, or hissing coming from the engine.
Loss of Power. ...
Poor Fuel Efficiency. ...
Engine Stalling. ...
Overheating. ...
Oil Leaks. ...
Check Engine Light.
How do you inspect a motor?
Where to look and what to look for
Scan the outside of the motor housing. ...
Check the convection cooling fan (if present) to make sure it's running.
Look at the windings. ...
Pop off the termination box cover and scan the connections. ...
Check bearing temperature.
How is motor testing done?
Using a multimeter, check to confirm the correct voltage is applied to the motor. Verify that the connection type is in good condition. For three-phase motors, the connection type is either star(Y) or delta. AC motor winding continuity test: Use a multimeter to check the continuity of the motor winding from each phase.
How do I know if my capacitor or fan motor is bad?
Signs of a bad AC capacitor include humming noises coming from the unit, slow starting or stopping of the fan motor, and frequent cycling on and off. AC capacitor troubleshooting should begin with checking for any visible signs of damage such as bulging capacitors or leaking fluid.
Can AC work without a fan?
Your AC is rendered useless without a functioning fan or furnace blower motor. This could also mean that you need a furnace repair or should start looking at costs for blower motor replacement. In addition, you will either suffer from no air or weak airflow with fan problems.
How much does it cost to replace a fan motor?
What's the Cost of Repairing or Replacing a Fan Motor? The average cost of a condenser fan motor is between $300 and $500 (not including installation). If the compressor breaks, you are looking at a much costlier problem which could cost up to $2000. In some cases, your fan motor may be under warranty.
What can cause a fan motor to go bad?
Overheating. Overheating is one of the most frequent occurrences that can render the blower motor inoperative. If the motor has overheated, it may shut itself down to prevent damage. You should keep your HVAC clean and clear of any blockages or debris to avoid overheating and maintain efficiency.
What causes a fan motor to burn out?
Generally, when power vent motors burn out early it is caused by a lack of intake ventilation. If there is not enough intake for the CFM rating of the power vent (CFM = cubic feet of air moved per minute), the fan will be working harder than it should.
How do you know if your motor needs to be replaced?
Below are signs when it's time for an engine replacement.
Your Car Is Constantly Overheating. ...
Your Car Has Performance Issues. ...
You Hear Frequent Knocking Noises. ...
Smoke Pours Out of Your Tailpipe. ...
There Are Metal Shavings in the Oil. ...
Your Check Engine Light Is On.
How to check if a motor is working or not?
Types of Electric Motor Tests
Electrical tests such as polarity checks and voltage level measurements.
Vibration tests to detect any imbalances or misalignments.
Thermal tests to monitor the motor's temperature to avoid overheating.
Dynamic tests to see how the motor performs in transient states.
What are the symptoms of a bad thermostat in a car?
Accurate Auto lists these signs below.
Odd Temperature Gauge Readings. Your temperature gauge should register cold when you first start your car and slowly build up to normal as the engine warms up. ...
Air Temperature Changes. ...
Coolant Leaks. ...
Strange Sounds. ...
Heater Problems.
What happens if the cooling fan fuse is blown?
Your car's cooling fan, or radiator fan, plays an important job in keeping your engine cool. Some of the most common causes of a faulty radiator fan include a blown fuse, a faulty temperature sensor, or a defective fan relay. If the fan stops working, your engine could overheat and be damaged.
How do I know if my fan is faulty?
The engine temperature rises to higher levels than normal, or remains lower than usual. This indicates a fan that's not working, working intermittently, or one that comes on at the wrong time. Causes include faulty sensors, bad temperature switch, defective control module, bad relay and blown fuse.