Compressor does not run (UT = 0 V)

Possible cause: Interruption in the connection cable between battery and electronics, main switch defective, or additional supply line fuse blown. Establish a secure connection, replace the main switch, or replace the inline fuse.

Compressor does not run (UT <= UOFF / Battery voltage too low)

Possible cause: Loose cable connections, poor/corroded contact, insufficient battery capacity, or cable cross section too small. Charge battery, tighten and clean cable connections, replace the battery, or upgrade cable cross-section according to the manual specification chart.

Compressor runs constantly

Possible cause: Thermostat sensor has no contact to the vaporiser, or thermostat is defective. Secure the thermostat sensor to the vaporiser or replace the thermostat.

Cooling capacity drops, interior temperature rises

Possible cause: Vaporiser iced over, ambient temperature too high, insufficient ventilation, or condenser dirty. Defrost the vaporiser, move the cooling device to a better ventilated location, or clean dust and impurities from the condenser.

Possible cause: Refrigerant circuit component cannot move freely (resting against the wall) or foreign body jammed between cooling machine and wall. Carefully bend the component away from the wall or remove the foreign body.

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Dometic • Compressor Built-in Cooling Device / Refrigerator

Dometic CoolMatic / RHD

Q: Compressor does not run (UT <= UOFF / Battery voltage too low)

Possible cause: Loose cable connections, poor/corroded contact, insufficient battery capacity, or cable cross section too small. Charge battery, tighten and clean cable connections, replace the battery, or upgrade cable cross-section according to the manual specification chart.

Q: Compressor runs constantly

Possible cause: Thermostat sensor has no contact to the vaporiser, or thermostat is defective. Secure the thermostat sensor to the vaporiser or replace the thermostat.

Q: Cooling capacity drops, interior temperature rises

Possible cause: Vaporiser iced over, ambient temperature too high, insufficient ventilation, or condenser dirty. Defrost the vaporiser, move the cooling device to a better ventilated location, or clean dust and impurities from the condenser.

Q: Loud humming noise

Possible cause: Refrigerant circuit component cannot move freely (resting against the wall) or foreign body jammed between cooling machine and wall. Carefully bend the component away from the wall or remove the foreign body.

Official technical documentation and workshop diagnostics for CoolMatic / RHD.

Technical Specifications

Electrical12 V DC or 24 V DC connection voltage. Power consumption: 45 W (CB-36, CB-40, RHD-50), 60 W (CB-110). Recommended external fuse protection: minimum 15 A for 12 V, minimum 7.5 A for 24 V. Cut-out voltage: 10.4 V (12 V system), 22.8 V (24 V system). Cut-in voltage: 11.7 V (12 V system), 24.2 V (24 V system).

Gas Or PressureRefrigerant circuit contains R134a.

Capacities DimensionsCapacities: CB-36 (36 l), CB-40 (40 l), CB-110 (100 l), RHD-50 (50 l). Ambient temperature range: -10 °C to +32 °C. Max air humidity: 90%. Max permanent inclination: 30°. Weights: CB-36 (17 kg), CB-40 (19 kg), CB-110 (28 kg), RHD-50 (20 kg).

Master Troubleshooting & Diagnostics Matrix

Error Code / Indicator	Symptom / Meaning	Step-by-Step DIY Fix	Suggested Actions
`N/A`	Compressor does not run (UT = 0 V) Possible Cause: Interruption in the connection cable between battery and electronics, main switch defective, or additional supply line fuse blown	Establish a secure connection, replace the main switch, or replace the inline fuse.	DIY Safe
`N/A`	Compressor does not run (UT <= UOFF / Battery voltage too low) Possible Cause: Loose cable connections, poor/corroded contact, insufficient battery capacity, or cable cross section too small	Charge battery, tighten and clean cable connections, replace the battery, or upgrade cable cross-section according to the manual specification chart.	DIY Safe
`N/A`	Compressor runs constantly Possible Cause: Thermostat sensor has no contact to the vaporiser, or thermostat is defective	Secure the thermostat sensor to the vaporiser or replace the thermostat.	DIY Check / Tech Fallback
`N/A`	Cooling capacity drops, interior temperature rises Possible Cause: Vaporiser iced over, ambient temperature too high, insufficient ventilation, or condenser dirty	Defrost the vaporiser, move the cooling device to a better ventilated location, or clean dust and impurities from the condenser.	DIY Safe
`N/A`	Loud humming noise Possible Cause: Refrigerant circuit component cannot move freely (resting against the wall) or foreign body jammed between cooling machine and wall	Carefully bend the component away from the wall or remove the foreign body.	DIY Safe

Frequently Asked Questions

Q: What does climate class of SN (Sub Normal) mean?

The climate class SN (Sub Normal) defines the intended ambient temperature range for the absorption fridge's optimal operation.

Q: What’s the cooling performance in warmer ambient temperatures?

Cooling performance for absorption fridges is affected by warmer ambient temperatures. Ensure proper ventilation around the unit as detailed in the manual to maintain performance.

Q: How to operate an RMxxxx with a solar panel?

To operate an RMxxxx series absorption fridge with a solar panel, ensure the solar system provides adequate 12V DC power or sufficient battery storage to handle the power requirements, particularly when running on DC mode.

Q: My RMxxxx needs to be replaced. What would be an alternative?

When replacing an RMxxxx series refrigerator, look for current Dometic absorption or compressor models matching the physical dimensions and energy source requirements of your motorhome cutout.

Q: The refrigerator does not work In AC power mode?

Check if the vehicle is properly connected to the AC mains supply, verify that the AC fuse in the motorhome is intact, and ensure the refrigerator is switched on to AC mode on the control panel.

Q: The refrigerator does not work In DC power mode?

DC mode (12V) typically only works while the vehicle engine is running and the alternator is supplying power, preventing the vehicle starter battery from draining. Check the 12V DC fuses, vehicle ignition connection, and input voltage at the refrigerator terminals.

Q: The refrigerator does not work In GAS mode?

Ensure the gas cylinder valve is open, the main gas shut-off valves in the motorhome are open, and there is no air trapped in the gas line (try igniting another gas appliance first). Check if the igniter is sparking and that the burner is clean.

Q: In automatic mode: The refrigerator is being operated with gas although it is connected to The AC power supply?

In automatic energy selection mode, if the AC voltage is outside the acceptable tolerance range or unstable, the control system automatically switches to gas mode as a safety fallback. Check the AC supply voltage and connections.

Q: The refrigerator is not cooling adequately?

Verify that ventilation grilles are not blocked, check that the thermostat is set correctly, ensure the door seals tightly, do not overpack the interior restricting airflow, and verify that the selected energy source (AC, DC, or Gas) is actively functioning.

Q: WARNING type fault messages

WARNING type fault messages indicate a non-critical operational issue or prompt. Consult the user manual for the specific warning code displayed on the 10-series control panel to take corrective action.

Q: ERROR type fault messages

ERROR type fault messages indicate a critical system failure that stops the refrigerator from functioning safely on the current energy source. Check the specific error code on the display, troubleshoot the underlying power, gas, or ventilation issue, or contact customer service.