Lennox High Limit Cycling / Overheating

Furnace short cycles; burners light for a few seconds to a minute, then shut off, repeating frequently.

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.

Possible Causes

Dirty Lennox air filter, Undersized or blocked return air, Closed supply registers, Oversized furnace for duct system

Safety: Turn off power before removing panels.

1. Replace filter: Install a clean, properly rated Lennox filter.
2. Open airflow paths: Open all supply and return registers and remove obstructions.
3. Check blower speed: Ensure blower is running at the correct speed for heating (technician may need to adjust taps or ECM settings).

Persistent short cycling can damage the heat exchanger; have a professional evaluate duct sizing and furnace capacity.

Medium 3/5

High Limit Switch

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