this normally closed (NC) thermal switch is rated to open at 250°F and automatically close at 220°F once internal temperatures return to a safe operating range

or the furnace short cycling—shutting down shortly after ignition before reaching the thermostat setpoint

When performing a York furnace ignitor replacement

70" WC rating is specific to the heat exchanger’s airflow requirements

return air

York S1-025-17620-017 Pressure Switch this normally closed (NC) thermalThe York S1 025 17620 017 Pressure Switch is a high limit safety control designed for precise HVAC system protection. Engineered for high pressure monitoring, this dual action pressure switch features a fixed 380 PSI open setpoint to prevent compressor damage and a 300 PSI close reset point for automated system recovery. As a genuine York OEM replacement part, it ensures seamless integration and provides the exact electrical specifications required