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How do you test a DC fan motor?

Author

Olivia House

Updated on February 23, 2026

How do you test a DC fan motor?

Check to make sure the DC motor's rotor can turn with no impediments. Switch the voltmeter to "Ohms". Attach one end of the red lead wires to the DC motor and run the DC motor's red wire to the battery. Attach the clip of the black lead wire to the DC motor and run the black motor wire to the battery.

Keeping this in consideration, how do I know if my DC motor is bad?

To test your DC motor, touch the leads of the ohmmeter to the leads of the motor. The meter's screen should indicate a low resistance (somewhere between 10 and 30 ohms), but if it reads an infinite ohms or an open circuit you should rotate the end shaft of the motor.

Similarly, how do you test the windings on a DC motor? The most common method used to check for shorted windings is to perform a drop test. In this test an ac voltage, normally 110 volts, is applied to the field leads. The voltage drop across each field pole is measured with a voltmeter. In a healthy motor, all voltage drops should be equal.

Correspondingly, how do you test a fan motor?

How to Test Your AC Fan Motor

  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.
  2. Check the windings. Next, check the windings of the fan motor for an open or a short.
  3. Inspect the capacitor.

How do you test a 12v DC fan motor?

Check to make sure the DC motor's rotor can turn with no impediments. Switch the voltmeter to "Ohms". Attach one end of the red lead wires to the DC motor and run the DC motor's red wire to the battery. Attach the clip of the black lead wire to the DC motor and run the black motor wire to the battery.

How do you test a fan?

If you want to see if your fan is properly amping up and down to control temperatures, simply download and run a CPU stress test while your fan speed application monitor is running. You should notice your fan speeds start to rise until reaching 100%.

How do I know if my electric motor is bad?

Check for shorts between the power wiring and ground. Select ohms resistance on the multi-meter and set for the 30,000-ohm range. Touch one lead to each motor power lead and the other to the metal motor casing. Any value less than about 0.2 mega ohms is a reason to discard the motor.

How do I test a fan motor with a multimeter?

If the shaft turns freely, set the multimeter to its ohms function. The windings (all three in a three-phase motor) should read low but not zero ohms. The smaller the motor, the higher this reading will be, but it should not be open.

Can you meg a DC motor?

Connect one lead of the DC motor to the megger probe and the other lead from the megger to the frame or metal case of the DC motor. Press the power button on the megger or turn the hand crank. The battery unit will take a few seconds to analyze the voltage travel and soon a reading should appear on the LCD screen.

How do you test a fan with a multimeter?

Take the black multimeter standard test lead and touch the white wire with it. 3. Touch and continue touching the white – brown wire with the red multimeter probe. Values measured in this step should be around point one or point two ohms.

What causes a DC motor to fail?

Low resistance is caused by the degradation of the insulation of the windings due to conditions such as overheating, corrosion, or physical damage. This leads to insufficient isolation between the conductors or motor windings, which can cause leakages and short circuits, and eventually motor failure.

What causes a DC motor to overheat?

Electrical overload caused by excessive voltage supply or overwork by drawing more current will lead to overheating issues. As the motor works harder or under unusual load, heat will be the chief byproduct, leading to failure. 2. Low resistance is the most common reason behind electric motor failure.

What causes a brushless motor to fail?

Heat is the number 1 cause of Brushless motor failure. You want to keep your motor temps around 150/160F. Around 175F the magnets start to demagnetize and you start losing power. The only other enemy of a brushless motor is dirt in the bearings.

What causes electric motor failure?

5 Things that Commonly Cause Electrical Motor Failures
  • High Temperatures and Heat. Exposure to high heat is a top culprit for all kinds of equipment failure and ranks as the number one reason for motor malfunctions and deterioration.
  • Exposure to Dust and Contaminants.
  • Power Surges and Other Supply Issues.
  • Excessive Humidity and Exposure to Moisture.
  • Over or Under-Lubrication.

How do you test an electric motor?

Check for shorts between the power wiring and ground. Select ohms resistance on the multi-meter and set for the 30,000-ohm range. Touch one lead to each motor power lead and the other to the metal motor casing. Any value less than about 0.2 mega ohms is a reason to discard the motor.

How do you check voltage on a DC motor?

Resistance can vary on a DC motor due to brush contact. The best way to measure resistance is to take several measurements and average. If possible, lock the rotor and then apply a small current to the terminals. Measure voltage and current and calculate R = V/I.

How do you test a motor?

Check for shorts between the power wiring and ground. Select ohms resistance on the multi-meter and set for the 30,000-ohm range. Touch one lead to each motor power lead and the other to the metal motor casing. Any value less than about 0.2 mega ohms is a reason to discard the motor.

Why did my fan randomly stop working?

Check the Fan Fuse
Like the circuit breakers in your house, these fuses are designed to break the electrical connection when too much electricity causes your fan to overheat. When the fuse melts, it breaks the connection and cuts power to the fan. Check the cord and the inside of your fan for this fuse.

How do I know if my fan relay is bad?

Symptoms of a Bad or Failing Cooling Fan Relay
  1. Engine running hot. One of the first symptoms commonly associated with a bad or failing cooling fan relay is an engine that runs hot or overheats.
  2. Cooling fans do not function. Non-functional cooling fans are another common symptom of a potential problem with the cooling fan relay.
  3. Cooling fans stay on at all times.

How do you test an electric motor coil?

The field if it has 4 wires will be built in 2 halves, each having two wires on them. There should be continuity between the wires on one coil winding but not across the two. If it has 2 wires there should be continuity between the wires but to no other metal on the coil.

What causes a DC motor to lose torque?

When a Series DC motor is overloaded it will lose torque as the rotation of the rotor is resisted, allowing Counter EMF to overcome applied voltage and decrease torque. Unless I have it backwards, In a shunt DC motor, when current to the shunt field increases, additional EMF is created reducing torque AND speed.

How do you check a motor short circuit?

How to Test Your Spindle Motor for Open or Short in Windings
  1. Set your multimeter to Ohms.
  2. Test T1 to T2, T2 to T3, and T1 to T3.
  3. If your spindle motor fails the test, you may want to make sure the problem is not with the connector, which may have coolant on it that's interfering with your results.
  4. Check your inserts.

How do you check fan motor winding?

Checking the windings on a motor using an ohmmeter. You want to see a resistance reading; either a zero reading or an infinte reading indicates a problem.

What causes armature failure?

  • Worn Commutators. Worn commutators are one of the most common causes of armature failure.
  • Excessive Vibration. A motor that is vibrating excessively can be the cause of a number of problems including.
  • Worn Carbon Brushes.
  • Burning Out.
  • Earthing / Grounding.