Lennox Capacity or Airflow Deficiency

The Lennox air conditioner runs continuously and struggles to reach the set temperature on very hot days.

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Possible Causes

Undersized system for home load, dirty coils reducing heat transfer, duct leakage in the attic or crawlspace, low refrigerant charge.

How to Fix / Troubleshooting

Safety: Turn off power before cleaning or sealing ducts.

  • 1. Clean indoor and outdoor coils: Ensure both coils are clean to maximize capacity.
  • 2. Seal accessible ducts: Use mastic or UL-181 foil tape to seal obvious leaks in accessible ductwork.
  • 3. Improve attic insulation and shading: Reducing heat gain can help an existing Lennox system keep up.
  • 4. Have charge and sizing checked: A technician can verify the refrigerant charge and confirm the system is properly sized for the home.

Note: Continuous running is not inherently harmful if airflow and charge are correct, but it indicates limited capacity.

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Repair Difficulty

Easy 2/5

Required Part

Lennox Condenser Coil
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