Dometic Air Conditioner: “E4”
warning RV air conditioner error codes
What it means
The outdoor temperature sensor (fitted on select heat-pump models) is reading open-circuit or out of range. Heat-pump operation is locked out, but the air conditioner (cooling), furnace, heat strip, and fan can still operate.
Most likely causes
- Disconnected, broken, or out-of-range outdoor temperature sensor most likely
- Loose or corroded outdoor-sensor wiring/connector common
- Failed control board sensor input less common
Safe checks you can do yourself
- Power-cycle the system at the breaker to check whether E4 is persistent.
- Confirm that cooling, furnace, and fan still work and only heat-pump mode is disabled, which matches an outdoor-sensor fault.
- If accessible, verify the outdoor sensor connector is seated; do not cut or splice wiring.
How to reset / clear E4
- Turn the thermostat OFF.
- Remove power at the AC breaker for about a minute, then restore.
- If E4 returns, the outdoor sensor or its wiring needs inspection.
When to call a technician
If E4 persists and you need heat-pump heating restored, have a technician test/replace the outdoor temperature sensor.
Applies to
Dometic Comfort Control Center 2 (CCC2) heat-pump-equipped systems · Dometic Single Zone LCD thermostat heat-pump systems (select models with outdoor sensor)
FAQ
What does Dometic Air Conditioner code "E4" mean?
The outdoor temperature sensor (fitted on select heat-pump models) is reading open-circuit or out of range. Heat-pump operation is locked out, but the air conditioner (cooling), furnace, heat strip, and fan can still operate.
How do I reset Dometic Air Conditioner E4?
Turn the thermostat OFF. Remove power at the AC breaker for about a minute, then restore. If E4 returns, the outdoor sensor or its wiring needs inspection.
What is the most common cause of E4 on a Dometic Air Conditioner?
The most likely cause is disconnected, broken, or out-of-range outdoor temperature sensor.
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Sources
- Comfort Control Center 2 Thermostat User's Guide — Section N, LCD Error Code (Error Code: E4) (Dometic Corporation)
- Single Zone LCD Thermostat User's Guide — LCD Error Code (Error Code: E4) (Dometic (via Prime Time RV component manuals))
Note: E4 applies only to systems fitted with an outdoor temperature sensor (heat-pump 'select models'). On non-heat-pump units this code is not expected.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.