HVAC Fan Continues to Run Slowly

HVAC Fan Continues to Run Slowly

key takeaways

If your HVAC fan continues to run slowly, it can be because of a failed capacitor or due to cracks and breakage in the fan belts. Sometimes, due to electrical connection and poor wiring, a fan will not turn. Breaker or thermostat problems can also cause low fan speed in your air conditioner. If your HVAC fan running slow, you can fix this by.

  • Checking the wire connection
  • Replace the belt if it is cracked
  • Clean the fan blades and filters
  • Clean all the blockages to get proper airflow

Reasons Why the Fan Speed May Be Slow in Your HVAC Blower

A defective or failed capacitor causes the fan motor to slow down or overheat. In most cases like this, the run capacitor must be changed. Normal wear and tear can cause fan belts to strain, crack, and break. This can result in a fan that turns slowly in your HVAC blower. If something in the motor fails, such as an electrical connection, poor wiring, or another operating issue, the fan will not turn.

Air Conditioner Fan Spinning Slow: Causes and Fixes

Your air conditioner fan spins slowly because of the malfunctioning capacitor. Outdoor AC fans include a few capacitors, which are similar to batteries and can store power so that the fan works consistently. If one of the capacitors fails, the fan will either stop working or fail to maintain the proper speed.

Breaker or thermostat problems can also cause the air conditioner fan’s slow speed.  If your AC fan isn’t spinning, it is because of a tripped circuit breaker or a turned-off thermostat. When a fan belt cracks or breaks, the fan cannot turn, even if all other components are working properly.

Another common cause of a fan not spinning properly is that it is not receiving the power it needs. In this case, it’s possible that a wire has become loose. If the system must operate at full power regularly to fulfill demand, the fan motor is more likely to fail.

If the air conditioner’s output does not match the size of your home, the system will be overworked. This can result in the AC fan motor burning out. 

Checking the wire connections is one of the first duties an AC technician takes on to fix this issue. If the belt is cracked, it is recommended to replace it with a new one.

Clean the fan blades and filter to ensure maximum speed. If there is some issue with a capacitor, you need to change it immediately to get the issue resolved. Clean all the blockages around the unit to get the proper airflow.

Make sure the unit is getting the proper power supply. If the unit is not receiving proper voltages, hire an electrician to get the issue fixed.

How to Test an HVAC Blower Motor

You can test an HVAC blower motor by using a multimeter. To test a blower motor using a multimeter, first select the “resistance” or “ohms” setting. Then, touch the multimeter probes to the blower motor terminals. If the resistance reading is infinite, this indicates an open circuit and a faulty blower motor.

If the resistance reading is 0, it indicates a short circuit and a malfunctioning blower motor. Finally, if the resistance reading falls within a specific range (often between 1 and 20 ohms), the blower motor is working properly. If you don’t have a multimeter, you can test a blower motor by attaching it to a power source, such as a battery, and checking if it turns on. If the blower motor does not turn on, it is faulty.

Blower Motor Only Works on Low Speed: What to Do

If your blower motor is stuck on low speed, several issues could be the cause:

  • Weak Capacitor: A weak capacitor may not provide enough power for higher speeds. Check the voltage to the motor during both cooling and heating modes. Monitoring amperage can also help diagnose the issue.

  • Blower Motor Resistor: The resistor controls the fan speed. If it’s defective, the fan might be stuck on low. Inspect the resistor for any visible damage, such as charring or melting, and test it with a multimeter. Replace it if necessary.

  • Wiring Issues: Loose or broken wires can interfere with the signals that control fan speed. Inspect the wiring connected to the blower motor, resistor, and control switch. Tighten any loose connections and replace any damaged wires.

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How to Test an AC Blower Motor: Step-by-Step Guid

Turn off the Power: Safety precautions should be taken carefully. So, firstly, turn off the power to the AC blower motor.

Take off the Access Panels: To reveal the internal structure, open the casing that covers the AC blower motor. This will assist you in determining the root cause of your motor’s failure or malfunction.

Test the Continuity of the Motor Circuit: The next step is to inspect the fan and motor for any visible damage. Then, using a multimeter, test the continuity of the two wires that carry electric current to the motor. Connect the red and black wires of the multimeter to the positive and black terminals, respectively.

Test the Thermostat: The thermostat’s signals control the blower motor. This suggests that if your thermostat is defective, your blower motor will not function. Check temperature settings on a programmable thermostat and fine-tune them to match the room temperature.

Checking the Motor Windings: Adjust a thermostat to test for resistance. Any broken wire in the winding will prevent the motor from working. The winding contains two terminals: A and B. And on these terminals, you will measure the resistance across the windings. Readings for a complete winding with no broken wires will be minimal. If it reads infinity values, there is a gap in the winding.

Checking the Capacitor: The blower motor frequently uses a capacitor to help start the motor. Set the multimeter to capacitance mode. Disconnect the capacitor and test its terminals to see if it has the correct charge (according to the manufacturer’s specifications).

Blower Motor Not Working on Any Speed: Diagnosis and Fixes

  • If there is any corrosion, breakage, or loose connections, the blower motor stops working. You should clean, repair, or replace the connector or wiring.
  • If the blower motor becomes too hot, it can shut off as a safety precaution. Ensure that the blower motor receives proper cooling and is not clogged by debris.
  • The HVAC control module is a computer that manages the HVAC system. If it fails, the blower motor stops working. You need to replace the HVAC control module.
  • The blower motor requires a reliable ground connection to function properly. A faulty ground connection can cause the blower motor to stop functioning. Check the ground connection for any problems and repair them if needed.

How to Check a Furnace Blower Motor for Issues?

To begin troubleshooting any electric motor, make sure that electrical power is reaching the motor at the proper voltage. Use a multimeter to check the voltage. Once you’ve confirmed that the necessary voltage is available to the motor and it still won’t start, turn off the power and examine the motor.

Rotate the motor shaft by hand to see if it is jammed. The load could be trapped, or the motor bearings can be defective or worn which prevents the shaft from turning. A loose or wobbling shaft indicates that the bearings are broken, preventing the motor from functioning properly. 

If the shaft revolves freely and smoothly, visually inspect any thermal protection mechanisms to ensure they are not tripped. If feasible, use a multimeter to confirm that the resistance across them is zero. This allows energy to freely pass to the motor windings.

People Also Ask

Why Is My Cooling Fan Running Slow?

Faulty wires and corroded or unclean connectors are among the possible causes of your cooling running slow. Reduced cooling fan speed can also be caused by a worn motor.

How Do I Fix Slow Fan Speed?

If your bearings become clogged with oil or debris, use a moist wipe to completely clean them. When you install a new ceiling fan, make sure all of the screws are tight. Do proper lubrication to the inside parts of your fan to maximize its speed. 

Why Is My AC Fan Speed Slow?

Run capacitors generate a revolving magnetic field in your system’s condenser fan. A defective or failed capacitor causes the fan motor to slow down or overheat. Cracked fan belts can also slow down the speed of the AC fan.

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