A furnace pressure switch is a safety gear located near the draft inducer motor of a gas-forced-air furnace.
The switch is there to prevent the furnace from running unless the correct venting air pressure is present.
Testing the furnace pressure switch itself requires amultimeterto check for voltage.
Gas Furnace and Water HeaterGetty / Jupiter Images
It often has a red faceplate.
Inspect the Pressure Switch Hose
Remove the main access panel on the front of the furnace.
If the hose is cracked, replace it.
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confirm the hose is not obstructed inside.
Do not blow into a hose that is connected, as this can damage the pressure switch.
Remove debris with a small screwdriver or similar tool, being careful not to poke into the switch body.
Do not blow into the inlet to remove the obstruction.
Reinstall the hose(s).
Clean the vents, if necessary.
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Set a multimeter to test for resistance (ohms).
Touch each tester probe to one of the switch terminals.
The pressure switch tester should read 0 or close to 0 (indicating no resistance).
If the reading is higher, the switch has failed and must be replaced by a qualified technician.
Test the Furnace Operation
Reconnect the wires to the pressure switch.
Reinstall the furnace access panel, and restore power to the furnace.
Test the furnace operation.
Appliances may have a few different types of switches, but not all have pressure switches.
Along withfurnacesandsome types of water heaters,washing machinesandwell pumpswill have pressure switches to modulate gas or water.
PF means “pressure fall.”
PR stands for “pressure rise.”
