Staff Answer
Sep 25, 2026 - 08:42 AM
Since the thermocouple, burner and tank are already done, look at the rest of the "stay lit" circuit. On the N400, the thermocouple runs through an interrupter before it reaches the gas valve. A bad interrupter or a loose or corroded connection anywhere in that circuit will make the flame drop out when you let go of the button. Clean and tighten each connection. The Norcold/Dometic Interrupter 621737 is in stock. Also make sure the new thermocouple tip sits right in the flame. If all of that checks out, the magnet in the gas valve itself may be weak. See our not staying lit on gas article and propane guide. The N400 is discontinued, and Norcold's current 3-way model is the Norcold N4150. See our Norcold replacement guide.
Since I can't confirm this 100% from here, please email us at info@rvfridgeguys.com or call 800-712-8822 with your model and serial number and we'll double-check it for you. You can also browse www.rvfridgeguys.com.
