Gas Furnace Pressure Switch Stuck Closed

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Gas furnace pressure switch stuck closed.

The board first checks the switch to ensure it is open prior to inducer call. If the switch is open the inducer starts and the resulting pressure change closes the switch. A gas furnace pressure switch closes to allow current to pass through and start the ignition of the furnace. If you have found that your pressure switch is not letting your furnace come on.

If you get a pressure switch code and the inducer will not come on remove one of the wires from the pressure switch. Pressure switch stuck closed. Watch this and we might be able to get it working again. If the inducer comes on the pressure switch is stuck closed.

The following example shows how this the furnace does a check for closed limits and an open pressure switch and proceeds with a gas valve switched off improper gas pressure settings etc 4 the inducer goes into a 30 second purge 5 the. Tapping lightly on the pressure switch body may open the switch and the unit may start. The pressure switch must be replaced. The furnace then runs awhile longer and this crazy cycle repeats pressure switch glitches open gas shuts off furnace starts another ignition cycle.

This is not a repair. If it is closed prior to call it will go into fault because the switch is clearly jumpered the circuit shorted or the switch failed closed. When the pressure switch opens the gas valve closes and the furnace starts another ignition cycle because the pressure switch closed after that 1 2 second glitch. As noted above the pressure switches used for gas furnaces are almost always normally open.

Only oem pressure switches should be used.