Danfoss High Limit Cycling / Overheating

Furnace starts normally but shuts down after several minutes with the blower continuing to run for a long time

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 filter, closed registers, undersized ductwork, blower speed too low, restricted heat exchanger

Safety first: Overheating can damage the heat exchanger. Address airflow issues promptly.

Steps:

Replace filter: Install a clean filter of the correct size and type.
Open registers: Ensure most or all supply registers are open to allow adequate airflow.
Inspect return air: Confirm that return grilles are not blocked and that doors are not creating closed-off rooms without returns.
Have blower speed checked: A technician can increase blower speed via the Danfoss control or motor wiring to reduce temperature rise.

Medium 3/5

High Limit Switch

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