Because this is an SPDT snap disc

What does it mean if my furnace is showing a pressure switch error

Durable Construction: Features a high-quality SPST switch mechanism designed for high-cycle industrial applications

ensuring perfect electrical integration and reducing troubleshooting time

Shaft failure typically results from overtightened drive belts causing excessive side-loading

Trane BLW1320 2 Stage Inducer Assembly R-410A Because this is an SPDTThe Trane BLW1320 2 Stage Inducer Assembly is a precise OEM replacement engineered for high efficiency gas furnaces. As a veteran technician knows, maintaining the pressure switch circuits integrity depends on the draft inducers ability to clear combustion byproducts effectively. This 115V single phase assembly operates at 2543 RPM, utilizing a 2 stage furnace inducer motor to modulate airflow based on heating demand. It serves as the direct BLW1320