The Dometic heat pumps aren't a replacement for the furnace and only operate in temps down to about 40 (F). So either the thermostat has a different mode setting to operate the furnace, or if it's a combined mode, it's failing to switch from heat pump to furnace.. Today the Dometic thermostat started reporting code E4, which means outdoor air temperature sensor fault. We don't have an outdoor temperature sensor. The heat and A/C still work. Our thermostat was replaced for this issue at the Rally last year, and we have camped for 3 to 4 weeks since then.

Dometic ECD
Dometic ECD
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic BordBar TB 08, Grå, 8 l, N (normal), E4,
Dometic BordBar TB 08, Grå, 8 l, N (normal), E4,
Dometic fridge showing E4 error dc out of range. Is
Dometic fridge showing E4 error dc out of range. Is
Dometic 3316230.000 Duotherm Single Zone Thermostat With Control Kit
Dometic 3316230.000 Duotherm Single Zone Thermostat With Control Kit
Dometic CT Thermostat Review John Marucci On The Road
Dometic CT Thermostat Review John Marucci On The Road
Dometic fridge showing E4 error dc out of range. Is
Dometic fridge showing E4 error dc out of range. Is
Dometic Optimus EActuator Optimus 3000 Series inboard electric
Dometic Optimus EActuator Optimus 3000 Series inboard electric
Dometic Rv Thermostat Wiring Diagram Dometic thermostat Wiring
Dometic Rv Thermostat Wiring Diagram Dometic thermostat Wiring
Dometic Frigo SBCKIT Standby cooling kit for Frigo R134a, hermetic
Dometic Frigo SBCKIT Standby cooling kit for Frigo R134a, hermetic
Dometic PerfectWall Adapter 012
Dometic PerfectWall Adapter 012
Dometic fridge showing E4 error dc out of range. Is
Dometic fridge showing E4 error dc out of range. Is
Dometic PerfectView RVMB2 Camera/display cable for MercedesBenz
Dometic PerfectView RVMB2 Camera/display cable for MercedesBenz
Dometic fridge showing E4 error dc out of range. Is
Dometic fridge showing E4 error dc out of range. Is
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic fridge showing E4 error dc out of range. Is
Dometic fridge showing E4 error dc out of range. Is
Diagnostic Code E4 Insufficient Capacity YouTube
Diagnostic Code E4 Insufficient Capacity YouTube
Dometic Büttner MT 1502MC Kit Complete solar system, 2 x
Dometic Büttner MT 1502MC Kit Complete solar system, 2 x
Dometic Refrigerator Error Code E4 costco mini fridge freezer
Dometic Refrigerator Error Code E4 costco mini fridge freezer
What Does E1 Code On Dometic Thermostat Mean How To
What Does E1 Code On Dometic Thermostat Mean How To
Dometic Refrigerator Error Code E4 costco mini fridge freezer
Dometic Refrigerator Error Code E4 costco mini fridge freezer
Dometic Refrigerator Error Code E4 costco mini fridge freezer
Dometic Refrigerator Error Code E4 costco mini fridge freezer
Dometic Adaptive Trim Tab System Kit 2.25
Dometic Adaptive Trim Tab System Kit 2.25" digital actuators
Dometic/Atwood RV Water Heater Thermostat Replacement (Too Hot OR Cold
Dometic/Atwood RV Water Heater Thermostat Replacement (Too Hot OR Cold
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic Thermostat E4 Code Troubleshooting Tips for Quick Fixes
Dometic fridge model RM1350SLMX error code E3 when hooked up
Dometic fridge model RM1350SLMX error code E3 when hooked up
Dometic Rv Thermostat Wiring Diagram
Dometic Rv Thermostat Wiring Diagram
Ask Dave What does an E7 error code mean on
Ask Dave What does an E7 error code mean on
Sealand Spring Cartridge Kit Replaces Dometic 385236096 For Traveler
Sealand Spring Cartridge Kit Replaces Dometic 385236096 For Traveler
How To Wire Dometic Rv Thermostat
How To Wire Dometic Rv Thermostat

The E4 code for the Dometic 3313192 thermostat is as we reported earlier. However, there is a second E4 code and it is for the Dometic CCC 2 thermostat. It says the same thing except it adds that the dehumidifier feature will be locked out as well. Everything else will function.. According to his profile, the OP has a 2018 model. I remember seeing this problem before, but darned if I can find it. I think resetting the thermostat will correct it. There is no external thermometer on a Montana so the E4 code is likely related to the thermostat having gone off the rails. _____