Hamworthy Air Pressure Switch S2 40-60 AA072573

The Hamworthy AA072573 is an air pressure switch rated S2 40-60, a sensing device used on Hamworthy boilers. It monitors the pressure differential created by the fan and flue system, confirming that air is moving correctly before the boiler is allowed to fire. The switch signals the control board once the required pressure is established, and interrupts the sequence when it is not.

• The boiler locks out during the ignition sequence even though the fan runs.
• Repeated lockouts that clear on reset but return on the next demand for heat.
• The fan runs continuously without the boiler progressing to ignition.
• Intermittent firing, with the boiler sometimes starting and sometimes failing on the same call for heat.
• A fault code relating to air pressure, fan proving or flue pressure is displayed.

• Confirm the appliance model and check the part number against the manufacturer's parts list for that model.
• Read the markings on the existing switch and compare the designation and pressure range with this part.
• Check the sensing tubes and fan for blockages or damage before assuming the switch itself has failed.
• Verify that the electrical connections and wiring to the switch are sound.