warning RV air conditioner error codes

What it means

The thermostat has lost its communication link with the air conditioner/heat pump control (power module) board. On the CCC2, if communication is lost with one zone the display shows E1 plus that zone number (and any other affected zones blink); if all module boards are lost, the whole system shuts down. On the Single Zone LCD thermostat, the display alternates between E1 and the previous mode and the system shuts down.

Most likely causes

1. Loose, unseated, or damaged RJ11/communication cable between the thermostat and the control box/power module board most likely
2. Corroded or dirty connector pins on the communication cable common
3. No power reaching the AC/heat-pump control box (tripped breaker, blown fuse, loose 12V/120V supply) common
4. Failed thermostat or failed power module / control board less common

Safe checks you can do yourself

• Cycle the system off and remove power: turn off the AC breaker and disconnect shore power, then wait a minute and restore power to force the thermostat and control board to re-establish communication.
• Inspect the thin communication (RJ11-style) cable where it plugs into the thermostat and into the rooftop/control box; reseat both ends firmly and check the small phone-style connectors for bent or corroded pins.
• Confirm the air conditioner control box actually has power (check the AC breaker and any inline fuse).
• Look for pinched, kinked, or rodent-damaged cable runs in the ceiling or wall chase.

How to reset / clear E1

1. Put the thermostat in OFF mode.
2. Remove all power to the system (turn off the AC breaker / disconnect shore power, and the 12V supply if applicable) for at least a minute.
3. Restore power; on the CCC2 a full system reset may be needed so the thermostat re-detects the zones and installed equipment (see the CCC2 user guide System Reset Procedure).

When to call a technician

If reseating the cable and power-cycling does not clear E1, or if you find damaged wiring, corroded boards, or suspect a failed control board or thermostat, have a qualified RV technician test and replace the affected component.

Applies to

Dometic Comfort Control Center 2 (CCC2) thermostat systems · Dometic Single Zone LCD thermostat systems · Rooftop Dometic / Duo-Therm RV air conditioners and heat pumps controlled by these thermostats

FAQ

Related · Dometic air conditioner

Sources

• Comfort Control Center 2 Thermostat User's Guide — Section N, LCD Error Code (Error Code: E1) (Dometic Corporation)
• Single Zone LCD Thermostat User's Guide — LCD Error Code (Error Code: E1) (Dometic (via Prime Time RV component manuals))

Note: Exact behavior differs slightly between the CCC2 (multi-zone, shows zone number) and the Single Zone LCD thermostat (cycles E1 with mode). Both confirmed from official Dometic user guides.

● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.