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The Goodman 20162906 M4 primary limit switch is a genuine OEM auto-reset high-limit control for AMH80603AXAA gas furnaces and compatible Goodman/Amana models. Mounted on the heat exchanger bulkhead, the primary limit monitors supply-air temperature and cuts the gas valve if the furnace overheats — typically from restricted airflow such as a dirty filter or failed blower. Once the temperature drops, this M4-style switch resets automatically, making it the furnace's front-line thermal protection.
OEM 20162906 is set to your furnace's exact cut-out temperature and mounting-bracket profile, ensuring correct protection and a clean fit. Generic limits with different trip points or bracket shapes can short-cycle the furnace or fail to seat properly. Match the OEM set point exactly on any primary limit.
Easy — two mounting screws and two spade terminals. Shut off power first. Plan 10–15 minutes. If the furnace keeps short-cycling on limit afterward, check the filter, blower, and ductwork for airflow restriction.