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The Goodman B1370198 Primary Limit Switch is the OEM high-limit safety control for the AMS81155CNA gas furnace. Mounted on the heat-exchanger bulkhead, it monitors supply-air temperature and opens the burner circuit if the plenum reaches its 150°F trip point — protecting the heat exchanger from cracking due to restricted airflow, a dirty filter, or blower failure.
The genuine Goodman B1370198 ships with the correct bracket geometry and a factory-matched 150°F set point. Universal limits frequently require bending or shimming to seat correctly against the exchanger, and mismatched trip temperatures lead to repeated shutdowns. For reliable, code-compliant operation, choose the OEM switch.
Easy (2/5). Removes with one or two screws and slides onto its spade terminals. De-energize the furnace and confirm airflow problems are corrected first — a limit that keeps tripping is usually a symptom of a dirty filter or failing blower, not a bad switch.
Note: This is a genuine OEM Goodman replacement part. National HVAC Parts is not affiliated with or endorsed by Goodman Manufacturing.