Comfortmaker: Pressure Switch Stuck Closed

What this fault means

The board saw the pressure switch already closed before the inducer started, treats it as a fault, and refuses to fire.

Likely causes

• Stuck pressure switch contacts
• Pinched or mis-routed tubing
• Control board input fault

What you can safely check

• Replace a dirty air filter — restricted airflow causes a surprising share of furnace faults.
• Confirm registers and the outdoor unit are clear of snow, leaves and debris.
• Cycle power at the switch once and let the system retry.

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