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HomeRepair HelpLennox Central A/C RepairLennox Central air conditioner is frequently cycling/short cycling Repair
Lennox Central air conditioner is frequently cycling/short cycling
If your Lennox central air conditioner is short cycling, it may turn on and off repeatedly, run briefly, or fail to complete a normal cooling cycle. The most likely cause is a clogged air filter, which restricts airflow through the furnace or air handler and can make the system overheat or shut down. Next, check for dirty condenser coils. Debris prevents the outdoor coil from releasing heat, which can cause the compressor to overheat and the AC to cycle too often. A failing wall thermostat or thermostat wiring is another possibility if its electrical contacts are intermittently sending power to the furnace, air handler, or condensing unit. Less commonly, a clogged filter can cause the evaporator coil to frost over, or a faulty control board may fail to power cooling components correctly. Replace the filter and clean the condenser coils only with power safely disconnected. Testing or replacing a thermostat and control board involves electrical work, while compressor, refrigerant, or sealed-system diagnosis requires an EPA 608-certified HVAC technician. Enter your Lennox model number to find the exact replacement air filter, thermostat, or control board for your central air conditioner.
01 - Lennox Central Air Conditioner Air Filter
Check and replace the air filter at least twice a year, more often in dusty/dirty environments or if there is a pet in the home. A clogged air filter will greatly reduce the air flow of the furnace or air handler which can result in the unit short cycling when trying to cool the home.
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Highly Likely
02 - Condenser Coils are Dirty
The condenser coils dissipate the heat as the refrigerant passes through the coils. If the condenser coils are dirty, they won’t be able to dissipate the heat as effectively. As debris builds up on the coils, the heat pump will become less efficient, causing the unit to work harder to cool down. If the coils are significantly dirty, the heat pump will not be able to remove the heat from the outdoor coil, resulting in the compressor overheating and short cycling. Check the condenser coils to determine if they are dirty. Refer to owner's manual for cleaning instructions.
Common
03 - Lennox Central Air Conditioner Wall Thermostat
The wall thermostat has electrical contacts that control the power supply to the furnace, air handler and condensing unit. If the contacts in the thermostat fail, the cooling system may turn on intermittently. To determine if the thermostat is defective, use a multimeter to test it for continuity. If the wall thermostat does not show proper continuity, replace it.
Less Common
04 - Lennox Central Air Conditioner Wifi Thermostat
The WiFi thermostat has electrical contacts that control the power supply to the furnace, air handler and condensing unit. If the contacts in the thermostat fail, the cooling system may run intermittently. To determine if the thermostat is defective, use a multimeter to test it for continuity. If the WiFi thermostat does not show proper continuity, replace it.
Less Common
05 - Clogged Air Filter
If the air filter is clogged, air cannot flow properly through the home's venting system. This greatly reduces the cooling capacity of the air conditioner. In addition, if the air filter is clogged, the evaporator coils will frost over and not be able to remove moisture from the air. The air filter should be checked and replaced at least twice a year, more often in dusty/dirty environments. Refer to owner's manual for guidance.
Less Common
06 - Lennox Central Air Conditioner Control Board
The control board regulates the power supply to all of the components of the furnace or air handler. If the control board fails, it might not send voltage to parts of the cooling system, causing a loss of cooling and frequent cycling.
Less Common
Frequently Asked Questions
Why is my Lennox central air short cycling?
Can a clogged air filter cause central air short cycling or an evaporator coil to freeze?
Can dirty condenser coils make my AC turn on and off repeatedly?
Could a thermostat cause my central air conditioner to short cycle?
How do I identify the correct Lennox AC replacement part?
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