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Why Is Your Air Conditioner Not Shutting Off?

When your air conditioner won’t shut off, it’s natural to worry about wasting electrical power as temperatures become too cool for comfort. When your air conditioning system keeps running and never seems to shut off, the problem could be linked to a number of malfunctioning componentsfrozen evaporator coils, a clogged air filter, a bad electrical relay switch that needs to be replaced, the fan blowing constantly, dirty condenser coils, a bad thermostat, or other problem with your HVAC system.

If your air conditioner won’t shut off, the issue likely stems from one of the following categories. Williams Comfort Air explains the reasons why your air conditioning unit doesn’t turn off and what you can do to correct the problem. If your air conditioner requires repair services from a professional technician, contact us to schedule an appointment or request emergency cooling repair.

Is It Ok for an Air Conditioner to Run All Day?

Even when the temperature outside is extremely hot, your air conditioner should not keep running around the clock. Cooling cycles should occur about two to three times per hour, lasting around 15 to 20 minutes each. Once the set temperature is detected by your thermostat, the air conditioning unit should power down, ending the cooling cycle.

If your cooling unit is constantly running for hours on end, immediate attention is needed. If you allow your air conditioner to keep running, electrical power is wasted and your system sustains excessive wear and tear, which causes damage to components and malfunctions which creates the need for parts or the entire system to be replaced.

Why Is My Air Conditioner Not Turning Off?

If your air conditioner doesn’t shut down as expected, the following issues may be present within your HVAC system.

Electrical Issues

Air conditioners have a number of electrical components. A stuck relay switch allows an electrical circuit to remain closed, constantly providing power to the air conditioner. The compressor contactor can fuse in a closed position, allowing the condenser unit to keep on running with constant power. Sometimes a stuck switch can be fixed, but typically you’ll need to have a technician replace the problematic switch.

Faulty Thermostat

Thermostats need to be replaced about every 10 years. Over time, thermostat sensors gather dirt, which prevents them from accurately reading the room temperature. Electrical wiring can be damaged and wiring connections loosen, which disrupts communication between the thermostat and the air conditioner.

Wrong Thermostat Settings

It may appear that your air conditioner constantly runs when only the system fan is on. Selecting the ON fan setting at the thermostat powers the blower motor and fan continuously instead of only when the cooling system cycles. You will hear the indoor components running and feel hot air blowing from your vents because the air conditioner isn’t on to produce cool air.

Also, it may seem as though your air conditioner is constantly running because the set temperature is different than expected. In households with multiple people making thermostat adjustments, the setpoint may be adjusted lower than usual, so the air conditioner will keep running to achieve this temperature even though you expect the system to turn off sooner.

Faulty Fan Limit Switch

Even when the correct fan settings are selected, the fan motor may continue running even when the air conditioner isn’t cycling. This can happen if the fan limit switch is stuck in the override position. Resetting the limit switch located near the blower fan will stop the fan from blowing unless directed by the thermostat.

Dirty Condenser and Condenser Coils

To cool a home, hot air passes over the indoor evaporator coil and heat is extracted. Refrigerant travels through the lines, running to the outdoor unit. It is pressurized by the compressor before moving into the condenser coil, where heat is released. Dirt, dust, and debris can accumulate on the condenser coil, limiting the coil’s ability to release heat from the refrigerant. If the condenser coils are too dirty, the air conditioner’s cooling power is limited so the system has to keep running in attempts to cool each room.

If the outdoor condenser unit is blocked by debris, there will not be enough air movement through the unit to release heat into the atmosphere. Grass clippings, bits of mulch, tall weeds, and other obstacles dirty up the fins and cause the condenser to become clogged. This problem prevents air from flowing properly so the unit will continue to operate as it desperately tries to generate enough cooling for your home.

Frozen Evaporator Coils

If the air conditioner is running yet you feel warm or hot air blowing from room vents, the evaporator coils may be frozen within the indoor furnace or air handler unit. System issues can prevent the evaporator coils from receiving enough heat, so condensation pulled from the air during the cooling process freezes on the surface of the coil. A layer of ice on the evaporator coils prevents refrigerant from absorbing heating energy in the air.

Frozen evaporator coils result from an excess of dirt buildup on the coil, a lack of air flow due to a dirty air filter or blocked room vents, or low refrigerant. Your evaporator coil may develop a heavy layer of ice if the condensate drip pan and drain line below are clogged, holding moisture within the system.

Dirty Air Filter

A dirty filter prevents air movement through the system, causing a number of problems as well as making it so the air conditioner won’t shut off. When the air filter is clogged with pollutants, the air conditioner has to keep cycling to provide enough cooling for the home.

Low Refrigerant Levels

Air conditioners are charged with specific refrigerant volumes to ensure correct cooling and comfortable indoor temperatures. If leaks in refrigerant lines, damaged coils, or faulty components allow refrigerant to escape the system, there is not enough refrigerant available to help the air conditioner absorb and transfer heat. The system will run for hours on end as it attempts to make up for this shortcoming.

Low Fan Speed

If the blower fan speed is too low, the system will be unable to move enough cool air into your home. If this should happen, your air conditioner will continue to cycle as it attempts to get cool air into your living areas. Dirt and grime caked on the fan blades can slow it down, restricting operation.

Incorrect System Size

Air conditioners come in many sizes, and fit is extremely important. When an air conditioning unit is too small or undersized, it doesn’t have enough power to achieve the temperatures you set for cooling. The system consumes a great deal of power, which is wasted providing inefficient cooling. The unit runs for hours without keeping the home at a comfortable temperature and will continue doing so until the entire unit is replaced.

What to Do When Your Air Conditioner Won’t Turn Off

If your air conditioner keeps on running and does not shut off, here are a few troubleshooting steps to try before you call a professional technician for repair services.

1. Adjust Thermostat Temperature Settings

Check the set temperatures on your thermostat – if the set temperature is lower than the current room temperature, the air conditioner cycle will not stop. Adjust the temperature up a few degrees higher than the current room temperature, which should trigger the thermostat to shut down the air conditioner.

2. Adjust Thermostat Fan Settings

Make sure the air conditioner is actually running and it’s not simply the fan running alone, making it appear as though a cooling cycle is constantly going. Check the fan settings on your thermostat – the toggle should be in the AUTO position so that the fan only runs while the air conditioner is on. If the thermostat fan setting is ON, move it to AUTO – with the temperature set above the current room temperature, the thermostat should tell the air conditioner to shut off as well as the fan.

3. Eliminate Air Flow Restrictions

Remove any obstacles that prevent air from freely flowing through the system, which can force the air conditioner to stay on longer than it should. Replace a dirty air filter with a clean filter, clean away dirt and debris that have accumulated along the outdoor condenser unit, and open all room supply vents throughout the home.

4. Clean the Blower Fan

A dirty blower fan restricts the cooling system’s ability to circulate cool air, causing the system to run continuously in efforts to cool the home. Remove grime that is restricting fan operation following these steps:

  1. Turn off electrical power to the indoor unit.
  2. Remove the access panel to the blower compartment.
  3. Remove the screws holding the circuit board in place. Keep wires connected and move the circuit board out of the way.
  4. Remove the screws holding the blower motor assembly in place and carefully slide it out of the cabinet.
  5. Use a soft brush to clean away debris on the fan blades. Vacuum debris from the blades and cabinet.
  6. Reposition the blower assembly in the cabinet and secure with screws. Reposition circuit board and screw into place. Replace the access panel. Restore power to the unit.

Call Williams Comfort Air for Air Conditioning Repair Service

If your air conditioner won’t turn off and you’re unable to fix the issue yourself, don’t wait to give us a call. A NATE-certified HVAC technician will diagnose the system issue and fix problem components or replace them right away.

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