In the case of a high-efficiency gas furnace that shuts down with an "open pressure switch" error, which of the following is NOT a proper troubleshooting step?

In diagnosing an "open pressure switch" error in a high-efficiency gas furnace, it's essential to understand the role of each component in the system. The pressure switch is designed to ensure that the proper negative pressure is present, which confirms that the induced draft fan is functioning correctly and that there is adequate venting for combustion gases.

Verifying gas pressure, inspecting the pressure switch itself, and checking the induced draft fan are all critical troubleshooting steps. Verifying gas pressure helps ensure that the furnace is receiving the appropriate amount of fuel for combustion. Inspecting the pressure switch is essential to determine if it is functioning correctly and not stuck in an open position due to debris or a malfunction. The induced draft fan must also be checked as it creates negative pressure in the flue system, which is necessary for the operation of the pressure switch.

Checking the furnace igniter, while important for diagnosing other issues related to ignition, does not play a direct role in troubleshooting an "open pressure switch" error. The pressure switch is concerned primarily with airflow and venting, and addressing the igniter first would not resolve the immediate issue related to the pressure switch's operation. Therefore, this step is not appropriate for troubleshooting this specific error.