When the pressure meets or exceeds the factory-set threshold, the switch closes its contacts and signals the control board that it is safe to proceed with ignition. Addressing filter changes, ensuring proper combustion air supply, and resolving minor venting issues promptly can significantly extend the life of the pressure switch and reduce the likelihood of unexpected lockouts during cold weather.
Step-by-Step Furnace Pressure Switch Diagnostic Procedures
Dirt, soot, or moisture in the flue gases can also clog the sensing port or tubing, causing the switch to open even when the draft is adequate. Replacement and Reset Procedure Replacing a pressure switch typically involves turning off power and gas, disconnecting the wiring and the vacuum tubing, and installing a new unit with the same pressure rating and electrical specifications.
How the Pressure Switch Protects Your Furnace Modern gas furnaces rely on a pressure switch to monitor the strength of airflow generated by the inducer motor. Diagnostic Steps Begin by inspecting the air filter and verifying that supply and return vents are fully open, then check the vent pipe for blockages or ice buildup that could affect draft.
Step-by-Step Furnace Pressure Switch Diagnostic Process
Common Failure Modes Over time, the internal diaphragm and contacts inside the pressure switch can wear out, especially in harsh environments with frequent short cycling. This small but critical component acts as a guardian, ensuring the blower and inducer motor create enough draft for proper exhaust before allowing the main burners to ignite.
More About What happens when a furnace pressure switch goes bad
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