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The Goodman B1370189 Primary Limit Switch is a genuine OEM high-limit safety control for the GMNT080-4B gas furnace and compatible Goodman/Amana models. Mounted on the heat exchanger or blower deck, this normally-closed switch opens at approximately 200°F to shut off the burners if supply-air temperature climbs too high — the furnace's primary defense against overheating from restricted airflow or a failed blower.
The OEM B1370189 is factory-calibrated to the 200°F trip point matched to your furnace's blower and heat-exchanger design. Generic limit switches with a different trip temperature can cause nuisance shutdowns or, worse, fail to protect the heat exchanger. For this critical safety device, OEM ensures correct protection and warranty compliance.
Easy (2/5). Allow 15–20 minutes. Disconnect power, photograph the wiring, remove the two mounting screws, transfer the spade connectors, and remount the switch flush against the panel. Restore power and verify the furnace completes a full heat cycle without tripping. If you are not comfortable working around gas appliances, hire a licensed technician.