How to Test Fujitsu Fan Motor: A Comprehensive Guide


Troubleshooting a Fujitsu fan motor can be a complex task, but with the right approach and tools, it can be done effectively. This comprehensive guide will walk you through the step-by-step process of testing a Fujitsu fan motor, from checking for physical obstructions to testing the control circuit and wiring. Whether you’re a DIY enthusiast or a professional HVAC technician, this guide will provide you with the technical expertise and practical knowledge needed to diagnose and address any issues with your Fujitsu fan motor.

Inspect the Fan Physically

how to test Fujitsu fan motorImage source: Fujitsu AC by Dinkun Chen

The first step in testing a Fujitsu fan motor is to inspect the fan physically. Check if the fan is caught, dropped off, or locked, and replace the fan or bearing if it is abnormal. This can be done by visually inspecting the fan and ensuring that it rotates freely without any obstructions.

Checking for Obstructions

Carefully examine the fan blades and the surrounding area for any debris or foreign objects that may be causing the fan to become stuck or impeded. Remove any obstructions and ensure that the fan can rotate freely without any resistance.

Inspecting the Fan Bearings

If the fan is not rotating freely, the issue may be with the fan bearings. Gently try to move the fan blades back and forth to check for any play or looseness in the bearings. If the bearings are worn or damaged, they will need to be replaced.

Measure the Fan Motor Resistance

Once you have confirmed that the fan is physically unobstructed, the next step is to measure the resistance of the fan motor. This can be done using a multimeter.

Preparing the Fan Motor for Resistance Testing

Before measuring the resistance, it is crucial to de-energize the fan motor. This means disconnecting the power supply to the motor to ensure your safety and prevent any potential damage to the multimeter.

Measuring the Resistance

Set your multimeter to the resistance (Ohm) setting and touch the probes to the terminals of the fan motor. The resistance reading should be within the range specified by the manufacturer. If the resistance is significantly different from the expected value, it may indicate an issue with the fan motor windings.

Check the Control Board Fuse

Another potential issue that can cause a Fujitsu fan motor to malfunction is a blown fuse on the control board. Use a continuity tester to check the 3.15 amp fuse on the control board.

Testing the Fuse

Disconnect the power supply to the unit and locate the control board. Use the continuity tester to check if the fuse is still intact. If the fuse is blown, replace it with a new one of the same amperage rating.

Test the Fan Motor Control Circuit

If the fan motor resistance is within the expected range and the control board fuse is functioning properly, the next step is to test the fan motor control circuit.

Using a Self-Made Tester

One way to test the control circuit is to use a self-made tester. This can be a simple circuit that applies a known voltage to the fan motor and measures the current draw. If the current draw is within the expected range, it indicates that the control circuit is functioning correctly.

Multimeter Testing

Alternatively, you can use a multimeter to check the control circuit. Measure the voltage at the fan motor terminals and ensure that it matches the expected voltage. Also, check the continuity of the wiring between the control board and the fan motor to ensure there are no breaks or shorts.

Troubleshoot the Control Board and Wiring

If the fan motor is not working, even after checking the physical condition, resistance, and control circuit, the issue may lie with the control board or the wiring.

Checking the Control Board

Inspect the control board for any visible signs of damage, such as burnt components or loose connections. If the control board appears to be faulty, it may need to be replaced.

Inspecting the Wiring

Carefully examine the wiring between the control board and the fan motor for any signs of damage, such as frayed or broken wires. Check the connections to ensure they are secure and free of corrosion.

By following these comprehensive steps, you can effectively test and troubleshoot a Fujitsu fan motor, ensuring that your HVAC system is functioning at its best.


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