Dometic RV thermostat error codes (E1, E4, E7) and how to reset

Common symptoms

• The screen flips back and forth between E1 and the mode you picked, and nothing runs.
• A zone number blinks on a CCC 2 thermostat.
• E7 appears and the whole system shuts down.
• The fan runs, but the AC won’t cool or the heat won’t come on.
• The AC cools fine, but heat pump mode won’t work, with E4 on the screen.
• Cooling is locked out with E5, while the furnace still works.

Quick checks before anything else

• Write down the code and, on a CCC 2, which zone it belongs to.
• Check the 120 volt AC breaker in the RV panel.
• Check the 12 volt fuse or breaker that feeds the thermostat and AC control.
• Make sure shore power is plugged in, or the generator is running and making power.
• Make sure the house battery is charged.
• Wait about 2 minutes after any change. All three Dometic models here delay the compressor that long.

Which Dometic thermostat do you have?

Dometic has used several wall thermostats in RVs, and the codes and the reset differ between them. Match yours by its looks and buttons:

What do Dometic thermostat error codes mean?

Each code tells you what failed and, just as useful, what still works while you wait for a fix.

• E1: lost contact The thermostat can’t talk to the control board in the AC. The system shuts down. Usually 12 volt power, 120 volt power or the cable.
• E2 and E3: indoor sensor The room temperature sensor reads open (E2) or shorted (E3). Heat and cool are locked out; the fan still runs.
• E4: outdoor sensor Only on some models. The heat pump is locked out; AC, furnace and fan still work.
• E5: freeze sensor The sensor that protects the cooling coil reads wrong. AC is locked out; furnace, heat strip, heat pump and fan still work.
• E7: no 120 volt power CCC 2 only. None of the AC control boards have 120 volt power, so the system shuts down.
• E8 and E9: setup error CCC 2 only. The DIP switches (tiny setup switches on the AC’s control board) are set in a combination that can’t work.

Step-by-step: fixing the most common codes

E1 and E7 start with power, so check power first. Codes that point to a failed sensor or wrong DIP switches need someone to open the ceiling unit, which has 120 volt parts.

1. Fix E7 by restoring 120 volt power On a CCC 2, E7 means none of the AC power module boards have 120 volt AC. Make sure the generator is running and making power, or that the shore cord is plugged in. Dometic says the cord should be sized to run the AC load. Then check the AC breaker in the RV panel. If you just had a breaker trip, see RV AC keeps tripping the breaker. If the RV has no 120 volt power anywhere, start with RV has no power when plugged in.
2. Fix E1 by checking 12 volt power The thermostat and the AC control board need 12 volt DC power to talk to each other. Check the 12 volt fuse or breaker for the AC and thermostat: the fuse should not be burnt and the breaker should be on. A low house battery or a converter that isn’t charging can also cut the 12 volt supply; our converter troubleshooting guide covers that. Then check the 120 volt side too, since Dometic lists both checks before calling for service.

   

3. Check the cable at the thermostat If you can see the plug on the back of the thermostat without pulling wires, make sure it is pushed in all the way. A loose or damaged cable between the thermostat and a control board gives E1. On a CCC 2, E1 with one zone number means only that zone lost contact; the other zones keep working.
4. Reset a CCC 2 after power problems Dometic says a CCC 2 needs a system reset after a memory loss or any DIP switch change. Put it in OFF mode. Press and hold MODE and ZONE together until the screen shows “IniT” and all the zones it finds. Let go, then press ON/OFF to exit. This brings back the factory settings, such as 72°F for cooling, so set your temperatures again.
5. Live with E4 until it is fixed E4 means the outdoor sensor on the roof unit reads open or out of range. Only the heat pump is locked out. Use the furnace or heat strip for heat, and keep using the AC for cooling. Don’t mistake normal heat pump behavior for a fault: Dometic’s single zone and CT heat pumps lock out below 30°F by design, and between 30 and 42°F a defrost cycle can blow cold air at the registers for a short time.
6. Use fan mode for E5, E2 and E3 With E5, cooling is locked out because the freeze sensor reads wrong. With E2 or E3, both heat and cool are locked out because of the indoor sensor. In all three, fan mode still moves air, and on a CCC 2 with more than one zone you can lean on the other units. These sensors sit inside the AC, so a tech has to test them.
7. Leave E8 and E9 to whoever set up the system These codes mean the DIP switches on one zone’s control board are set wrong, for example heat pump and heat strip both switched on. They come from how the system was set up during install or service. The switches are in the ceiling unit next to 120 volt wiring. After a tech corrects them, do the IniT reset so the thermostat reads the new settings.
8. Collect the numbers before you call Dometic asks for the AC model and serial number from the label on the base pan, which you see by removing the return air cover, plus the part and serial number on the electronic control kit in the same cavity. With those and the code, a shop can order the right sensor or board.

Resets and differences by model

CCC 2. OFF mode, hold MODE and ZONE until “IniT”, release, press ON/OFF. Factory settings come back. Dometic treats this as the fix for memory loss and DIP switch changes.

Single Zone LCD. Dometic lists a system initialization that the installer does after setup: with the thermostat off, hold the + button, then also hold On/Off Mode for three seconds, then press On/Off Mode again to turn it off.

CT Capacitive Touch. The installer initialization is similar: thermostat off, press the + button and hold the On/Off Mode button for three seconds until the screen shows “- -“.

On all of them, a short power cut does not erase your settings: Dometic says the system restarts with the previous set points when power returns. Full code lists with every check are in our Dometic CCC 2 code list and Single Zone LCD code list.

When to call an RV tech

• E1 stays after you confirm 12 volt and 120 volt power and the cable plug.
• E7 stays with good power at the RV panel.
• Any E2, E3, E4, E5 or E6 code, since the sensors sit inside the AC near 120 volt parts.
• E8 or E9, which need the DIP switches reset.
• The thermostat stays blank with good 12 volt power.

For how the thermostat, control board and roof unit fit together, see our RV AC repair guide.

Common questions