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The Goodman 20162906 M4 Primary Limit Switch is a genuine OEM high-limit safety control for the Goodman GCH90905DXAB gas furnace. Mounted on the heat exchanger, this thermal switch opens the circuit and shuts down the burners if the plenum temperature exceeds its rated set point — protecting the furnace and home from overheating.
OEM Goodman limit switches are calibrated to the exact trip temperature specified for this heat exchanger, ensuring proper safety response. Generic switches may carry different set points or reset behavior, risking short-cycling or, worse, failure to trip. As a primary safety device, OEM replacement is the recommended choice.
Easy (2/5). Two mounting screws and quick-connect terminals — usually a 15-minute repair. Cut power at the disconnect before servicing and match the switch orientation to the original.