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The Goodman 20162906 M4 Primary Limit Switch is a genuine OEM auto-reset high-limit control for the AMVM970803BNAA modulating gas furnace and related Goodman, Amana, and Daikin units. Mounted on the heat-exchanger / blower deck, this primary limit senses supply-air temperature and opens the control circuit if the furnace overheats — typically from a dirty filter, closed registers, or a failing blower. When temperatures return to normal it resets automatically, restoring heat without a service call for routine airflow events while still protecting the heat exchanger from thermal damage.
The OEM 20162906 carries the exact trip temperature, probe length, and mounting footprint engineered for this furnace. A universal snap-disc with the wrong setpoint or insertion depth will short-cycle the furnace or allow it to overheat. Match the OEM part for correct, safe operation.
Moderate (2/5). Cut power, remove the two wire terminals and mounting screws, and install the replacement in the same orientation. Verify with a multimeter and address any airflow restriction (filter, coil, blower) so the new limit isn't tripping a real fault.