Dometic and Furrion RV AC Error Codes Explained (E1 to E9)
Posted by RV AC Guys on 22nd Oct 2026
What your RV AC thermostat is trying to tell you
When an RV air conditioner stops working, the wall thermostat often shows a short code instead of the temperature. Those codes point to the problem, but the manuals that explain them are hard to find. Here's what the common Dometic and Furrion codes mean, taken from the manufacturers' thermostat manuals, plus what to check first.
Two rules apply to almost every code: check power first (12 volt DC to the thermostat and 120 volt AC to the air conditioner), and wait about 2 minutes after a reset, because the compressor has a built-in restart delay.
Dometic Comfort Control Center 2 (CCC2) codes
| Code | What it means | What still works | Check first |
|---|---|---|---|
| E1 | Thermostat lost communication with the AC control board(s). If only one zone is affected, E1 shows with that zone number. | System shuts down | 12V at the thermostat, the thermostat cable and its connectors, and the control board in the affected AC |
| E2 | Indoor temperature sensor open or out of range | Fan only | Sensor connection at the control board |
| E3 | Indoor temperature sensor shorted | Fan only | Sensor wiring for pinches or damage |
| E4 | Outdoor temperature sensor open (select models) | Everything except the heat pump | Outdoor sensor and its connector |
| E5 | Freeze sensor open or out of range | Heat works; AC is locked out | Freeze sensor on the evaporator coil |
| E7 | No 120V AC power reaching the control boards | System shuts down | AC breaker, shore power or generator, and campground voltage |
| E8 | Heat pump and heat strip DIP switches are both on in one zone | Setup error | DIP switch settings on the control board |
| E9 | Dehumidify DIP switch is on together with the heat pump or heat strip switch | Setup error | DIP switch settings on the control board |
E1 is the code we hear about most. Low battery voltage, a loose thermostat cable or a corroded connector cause it far more often than a failed board, so check those before buying parts. If you do need one, see our Dometic thermostats, Dometic control boards and Dometic sensors. The Dometic CCC2 / FreshJet wall thermostat 9610007991 works with single-zone and multi-zone systems.
Dometic single-zone LCD thermostat codes
Dometic's single-zone LCD thermostat uses codes E1 through E5 with the same meanings as the CCC2: E1 lost communication, E2 and E3 indoor sensor open or shorted, E4 outdoor sensor open (select models), and E5 freeze sensor open. Dometic also says to clean the air filter at least every two weeks of use, because a clogged filter is a common cause of freeze-ups.
Furrion Chill thermostat codes
| Code | What it means | Check first |
|---|---|---|
| E1 | Indoor temperature sensor fault (on the FACW10ESSA-BL, the control box indoor sensor) | Sensor connection at the control box |
| E2 | Evaporator temperature sensor fault | Evaporator sensor and its connector |
| E3 | Thermostat lost communication with the control box | 12V supply, thermostat cable, and campground voltage |
| E6 | Thermostat indoor sensor fault (FACW10ESSA-BL) | The thermostat itself |
| lo | 12V supply to the thermostat is too low | House battery and converter charging |
Furrion's manuals say these codes shut the system down until the fault clears. Low campground voltage is a commonly reported cause of E3. Parts are on our Furrion air conditioner parts page, including control boxes.
What about Coleman-Mach codes?
Coleman-Mach's 9330 zone thermostat shows "Er" when the temperature reading is out of range or a remote sensor has failed, and a flashing "GAS" simply means the furnace is helping the heat pump. On the control box, a green LED that flashes and then stays steady is normal; if it's off, 12V control power is too low, and the system won't run below 9.75 volts DC. Coleman-Mach doesn't publish an E-code list for its 9430 and Bluetooth thermostats, so be wary of code charts online that claim to. For Coleman-Mach help, see our posts on troubleshooting a Coleman-Mach and resetting a Coleman-Mach.
When it's time to call a tech
- The same code comes back right after you've checked power and connections.
- You smell burning, or the breaker trips again as soon as you reset it.
- The fix means opening the rooftop unit and you aren't comfortable working near 120 volt wiring and capacitors.
For a free, brand-by-brand reference of AC and furnace codes, see RV Guidance: RV Air Conditioners and Furnaces.