Lennox Short Cycling Due to Control or Sizing Issues

Lennox air conditioner short cycles, turning on and off every few minutes without reaching set temperature.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Oversized condenser relative to home load, Thermostat located in draft or direct supply air, Dirty evaporator coil causing freeze/thaw cycles, Low-pressure or high-pressure safety cycling

How to Fix / Troubleshooting

Safety: Turn off power before moving thermostat wiring or opening equipment.

  • 1. Check thermostat placement: Ensure the thermostat is on an interior wall away from supply vents, windows, and heat sources. Relocate if necessary.
  • 2. Verify filter and coil cleanliness: Replace filters and clean coils to prevent freeze-up that can cause cycling.
  • 3. Adjust thermostat settings: Increase the temperature differential or cycle rate if available in the Lennox thermostat installer menu.
  • 4. Have safeties checked: If the outdoor unit is cycling on pressure switches, a technician must diagnose refrigerant and airflow issues.

Note: Chronic short cycling reduces efficiency and compressor life.

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Repair Difficulty

Medium 3/5

Required Part

Lennox iComfort Thermostat
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