Multi-split air conditioners have one outdoor unit and multiple indoor air handlers. Each indoor zone has an air handler and a thermostat that work together to control the temperature in the space. Therefore, if one zone isn't cooling down while the rest of the home is receiving cool air, the affected zone's air handler may be faulty. Below are three reasons the air handler isn't working and tips on how to fix it.
Each air handler has a thermostat that signals the unit to turn on and cool the space to the desired temperature. If the thermostat is defective or has faulty sensors, it may fail to detect the ambient temperature. Therefore, it won't signal the air handler to turn on and cool down the zone. Thermostats usually develop mechanical and electrical issues due to the buildup of dirt, dust, and debris. Improper installation can also cause the device to send false signals to the air conditioner. Therefore, replace the thermostat to restore efficient cooling in the zone.
Dirty or Frozen Evaporator Coils
AC evaporator coils are located inside the air handler. They carry refrigerant, which enables them to absorb heat from the indoor air. If the coils are dirty, the layer of dirt acts as insulation, preventing the refrigerant from absorbing heat from the air. This hinders cooling, despite the air handler working properly. If your evaporator coils are dirty, clean them to allow the refrigerant to cool the air.
Evaporator coils can freeze if there's an airflow blockage due to dirty filters or a dirty air handler. Frozen coils cannot absorb heat from the air, as freezing disrupts heat exchange between the air and the refrigerant. Therefore, the unit will blow warm air into the zone. If your evaporator coils are frozen, turn off the handling unit to prevent it from overheating.
Faulty Fan Motor
Each indoor air handler has a blower fan that is powered by an electric motor. The fan blows air over the evaporator coils, so the refrigerant can absorb the heat. If the fan motor has malfunctioned due to overheating or electrical issues, it won't power the fan. Thus, the air handler will not be able to blow warm air over the evaporator coils. If you don't hear a low humming sound coming from your air handler, it means the fan isn't running. Repair the motor and check the fan blades for obstructions caused by dirt and debris.
If one of your air handlers isn't working, turn off the air conditioning in the affected zone to protect the handler's components from overheating and getting damaged. Contact an air conditioning contractor for a professional diagnosis and repair.
To learn more, contact a professional AC repair service in your area.