Troubleshooting a Gas Furnace Pressure Switch
Troubleshooting a Gas Furnace Pressure Switch
The pressure switch on a furnace may fail or get stuck in an open position. To test for proper functioning of the furnace pressure switch, you will need a multimeter (voltmeter/ohm-meter), a thermostat at a setting calling for heat, and the switch’s power wiring leads disconnected from the pressure switch terminals.
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For each of the switch’s two terminals, the pressure switch ohm meter should read 0 or close to 0 (no resistance) when the ohm meter leads are placed on each of their respective switch terminals.
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A resistance reading of infinity or a large number means pressure switch failure.
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Another method is to use a volt-meter where the voltage should read between twenty-four to twenty-eight volts DC between each terminal and ground.
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You should also check for a clogged hose port at the draft inducer or cracked or broken hose(s) running from the pressure switch to the draft inducer or condensate collector box which can cause a tripped switch (failure) condition.
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