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A member experienced simultaneous failures of both the furnace and rear A/C heat pump in their 2021 3121RL with iNCommand during cold weather, leaving only electric heaters as backup. The furnace would run the fan and open the gas valve but failed to ignite, despite replacing the igniter and confirming other components were functional. The rear A/C heat pump also stopped responding to iNCommand controls. Community members suggested a hard reset of the iNCommand system, checking the igniter...
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A member experienced simultaneous failures of both the furnace and rear A/C heat pump in their 2021 3121RL with iNCommand during cold weather, leaving only electric heaters as backup. The furnace would run the fan and open the gas valve but failed to ignite, despite replacing the igniter and confirming other components were functional. The rear A/C heat pump also stopped responding to iNCommand controls. Community members suggested a hard reset of the iNCommand system, checking the igniter gap, inspecting the burner for rust, and verifying the propane regulator’s performance. It was discovered that the furnace’s outside reset switch must be on to supply 12V power to the zone 2 A/C, a wiring quirk confirmed by others.
Ultimately, the issue was resolved by removing and inspecting the furnace, revealing significant rust in the firebox and burner. Replacing the burner and gas valve restored heat, and a disconnected flex-duct was also fixed. The original poster shared that Dometic has discontinued a key mounting bracket, but cleaning and repainting the existing one worked. ASA Electronics provided helpful wiring documentation for the iNCommand system, which was added to the member’s reference library.