Lennox A/C Troubleshooting Flowchart

Is your air conditioner... The problem might be your... What's wrong? How you can fix it
Thermostat Dead batteries may be the cause, or the thermostat may be on the wrong setting. Replace the batteries and ensure that the thermostat is set to cool.
Circuit breaker The breaker switch may be turned off. Flip the switch back to the “on” position.
Not blowing cold air? Air filter The filter may not be effective if it is full of debris. Change or clean the air filter if you haven’t done so in a while.
Outside unit The air conditioner unit may be unable to vent hot air out properly if there is debris in the way. Clear out vegetation and leaves from near your unit, ensuring that you have at least 2 feet of clear space around your A/C.
Refrigerant Leaking refrigerant means that your unit is less efficient and won’t cool well. Call an HVAC technician to address this problem.
Insulation Inadequate insulation in the walls, windows or doors means that cool air can leak out while hot air gets trapped. Windows are common spots where air leaks out. Think about upgrading to insulating windows or use blackout curtains.
Dripping water? Condensate line The PVC pipe that exits your air conditioner may be blocked. Use compressed air to remove the blockage.
Drain line If the drain is clogged, water will end up overflowing from the drain pan and can get into internal parts and cause damage. Check the line and remove the clog before it causes more problems.
Making odd sounds? Blower motor or belt Squeaking sounds may mean that there’s an issue with the belt or blower motor. Applying lubricant can help the parts run better.
Fan blades If the sound is like a card stuck in a bicycle spoke, there may be something caught in the fan blades. Turn off power to your air conditioner and check if there is debris between the blades and carefully remove it.