York S1-024-35978-000 Pressure Switch

The York S1-024-35978-000 Pressure Switch is a critical safety component designed for precise differential air pressure monitoring in York, Coleman, and Luxaire gas furnaces. Built to exact OEM specifications, this switch features a set point of -.67" WC (Water Column). As a Single Pole Normally Open (SPNO) device, the internal switch action is configured to close on fall, ensuring the combustion process only continues when the draft inducer motor maintains the required negative pressure. This prevents hazardous operation during venting obstructions or inducer motor failure.

For technicians troubleshooting a furnace that is not cycling or is locking out with a three-flash or four-flash error code, this genuine OEM repair part ensures a direct drop-in replacement. Its robust construction is engineered to withstand the rigorous cycling of modern condensing furnaces. Using a certified furnace pressure switch with the correct WC rating is essential for maintaining the system's AFUE rating and overall operational safety. Always verify the pressure differential and model number compatibility before installation to ensure the safety limit circuit functions as intended by the manufacturer.

• Precise Calibration: Factory-set at -.67" WC to ensure accurate vent pressure detection and system safety.
• OEM Compatibility: Designed specifically for York CM9M100C16MP11A and related models, eliminating universal mount vibration issues.
• High-Reliability Contacts: SPNO contact form designed for thousands of cycles without carbon buildup or sticking.
• Safety Compliance: Directly interfaces with the furnace control board to prevent ignition if the inducer path is restricted.

What does 'Close on Fall' mean for this York S1-024-35978-000 switch?
In HVAC applications, 'close on fall' means the electrical circuit completes when the negative pressure (vacuum) reaches the designated set point of -.67" WC. If the pressure fails to drop to this level, the switch remains open and the ignitor will not glow.

Can I use a pressure switch with a different WC rating if it looks the same?
No. Using a switch with a different Water Column rating can lead to premature furnace failure or dangerous operating conditions. Always match the S1-024-35978-000 exactly to ensure the safety limits are maintained.

How do I test if this pressure switch is failing?
Use a digital manometer to measure the actual vacuum from the draft inducer port. If the pressure exceeds -.67" WC but the SPNO contacts do not show continuity on your multimeter, the internal diaphragm or switch has likely failed.

Disclaimer: While we strive for 100% accuracy, product data and specifications are subject to change. Please contact our team to confirm compatibility or technical details before purchasing.