Dometic CCC2 thermostat fault codes
Dometic's networked thermostat for Penguin, Brisk and Blizzard rooftop units. The thermostat talks to a control box in the ceiling assembly over a data cable; the box switches the 120V. Fan-only keeps working through most sensor codes, which proves the box is alive.
Dometic CCC2 code E1
Lost communication between thermostat and the rooftop control box. Reseat both ends of the data cable (one end is under the ceiling shroud). Look for a pinched cable at a slide or the ceiling. Try a known-good cable; replace the control box if the cable is good.
Dometic CCC2 code E2
Indoor temperature sensor open or out of range. Reseat the sensor plug at the board. Ohm the thermistor (about 10 kΩ at 77°F). Replace it.
Dometic CCC2 code E3
Indoor temperature sensor shorted. Reseat the plug, ohm the sensor, replace it.
Dometic CCC2 code E4
Outdoor temperature sensor open or out of range (heat pump models). Reseat, ohm, replace.
Dometic CCC2 code E5
Freeze sensor open or out of range. Reseat, ohm, replace. Check the coil for ice while you are there.
Dometic CCC2 code E6
Humidity sensor open. Reseat or replace the sensor.
Dometic CCC2 code E7
Loss of 120V to the rooftop unit. Breaker, the plug in the ceiling box, voltage at the unit. The thermostat (12V) stayed alive, the AC didn't.
Dometic CCC2 code E8
Invalid zone configuration: DIP switches. Each rooftop board needs a unique zone on its DIP switches. Set them per the manual and power cycle.
Dometic CCC2 code E9
Invalid zone configuration. Same as E8: check the DIP switches on every board, power cycle, re-pair.
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Full field guide: Dometic CCC2 thermostat
Codes come from the maker manuals and public service sheets. Your model's own chart always wins, and LP and 120 volt work belongs to a qualified technician.