An air conditioning (AC) fan that won’t turn off can be both frustrating and costly, as it can lead to increased energy consumption and wear and tear on your system. Here are some steps you can take to diagnose and potentially fix the issue if your AC fan won’t turn off:
1. Check the Thermostat Settings
The first step is to inspect your thermostat settings.
Ensure that the fan setting is not set to “ON,” which keeps the fan running continuously. Instead, set it to “AUTO,” which should make the fan run only when the cooling or heating system is active. If the thermostat is set correctly but the fan still won’t turn off, proceed to the next steps.
2. Inspect the Thermostat Wiring
Sometimes, faulty wiring in the thermostat can cause the fan to run continuously. Turn off the power to your HVAC system to avoid any electrical hazards. Remove the thermostat cover and check for any loose or frayed wires. Tighten any loose connections and replace any damaged wires. If you’re unsure about handling electrical components, it’s best to call a professional technician.
3. Examine the Fan Limit Switch
The fan limit switch, located inside the furnace or air handler, controls when the fan turns on and off. If this switch is stuck or malfunctioning, it could cause the fan to run non-stop. To check the fan limit switch, turn off the power to the HVAC system, open the furnace or air handler access panel, and locate the switch. Gently press the reset button if it has one, or ensure the switch is set to “AUTO.” If the switch appears damaged or defective, it may need to be replaced.
4. Check for Stuck Relay Switch
The relay switch in the control board can sometimes stick, causing the fan to run continuously. Locate the relay switch, which is typically found on the control board inside the furnace or air handler. Listen for any clicking sounds when you manually turn the thermostat fan setting from “ON” to “AUTO.” If the relay switch is stuck, it may need to be replaced by a professional HVAC technician.
5. Inspect the Control Board
A malfunctioning control board can also cause the fan to keep running. The control board manages the overall operation of your HVAC system. If you suspect the control board is the issue, it’s crucial to consult with a professional technician, as diagnosing and replacing a control board requires specific expertise.
6. Professional HVAC Service
If you have gone through these steps and the fan still won’t turn off, it’s time to call in a professional HVAC technician. They can perform a comprehensive inspection, accurately diagnose the problem, and make any necessary repairs. Continuing to run your AC fan without addressing the underlying issue can lead to higher energy bills and potential damage to your HVAC system.