Amana, a division of Whirlpool Corp., is an American residential appliance manufacturer that's been in business since 1934. The company offers an extensive line of home heating options, including furnaces. Amana gas and oil furnaces use an internal safety component known as a pressure switch to monitor the appliance for venting obstructions. The pressure switch opens and closes to energize or deactivate the induced draft blower. Occasionally, the switch gets stuck in the open position, allowing the blower to run continuously. Troubleshoot an open pressure switch when the control board diagnostic lights flash three times between pauses.
Attempting to repair the furnace while it's connected to a power source may result in serious injury or death. Always disconnect the electrical supply to the furnace before troubleshooting or servicing any of its internal components. You can shut off the electricity from your electrical service panel or fuse box. Remove the fuse that supplies the power to the appliance or flip the corresponding circuit breaker switch to the "Off" position. The burner compartment service panel is held to the furnace cabinet with several screws; the type and number of screws varies by model. Unfasten the screws and set aside the removed panel.
A disconnected pressure switch hose is the first thing you should check when your furnace registers an open pressure switch error. Locate the pressure switch mounted to the wall of the burner compartment, just above the gas burners. There should be a thin hose attached to the side of the pressure switch component; reattach the hose if you see it dangling from the induced draft blower at the top of the compartment. While you're there, check the pressure switch wiring as well. Examine the wires for possible damage and make sure they're connected to the switch terminals.
Restricted airflow can also cause the furnace pressure switch to malfunction. It's a good idea to check the air intake, flue piping and outdoor exhaust vent for blockages each time the furnace registers an open or closed pressure switch error. Detach the pressure switch hose from the induced draft blower and pressure switch component. Ensure that the inside of the hose is completely clear before reattaching it. Make checking the venting a regular part of your furnace maintenance to avoid future pressure switch errors.
If the pressure switch hose was connected and you were unable to find any venting obstructions, the switch may simply be faulty. You can test the switch with a digital multimeter to be sure. Detach the wiring from the pressure switch terminals. Set the multimeter to read "Rx1" resistance and touch the probes to the empty terminals. The multimeter should read "0" if the switch is functional. Replace the switch if you receive a different reading; just unfasten the mounting screws to free the faulty component. Install the new pressure switch in its place and attach the removed wires to the component terminals.