Dometic RM123
Official technical documentation and workshop diagnostics for RM123.
Technical Specifications
Master Troubleshooting & Diagnostics Matrix
| Error Code / Indicator | Symptom / Meaning | Possible Cause | Step-by-Step DIY Fix | Suggested Actions |
|---|---|---|---|---|
N/A | The fridge won't run on gas | The gas bottle is empty, or an LP-gas valve is closed. | Check the gas bottle isn't empty, and that every LP-gas valve is open. | DIY Safe |
N/A | The fridge won't run on 12V | The 12V supply is disconnected, its fuse has blown, or the 12V switch is off. | Check the 12V supply reaches the fridge, its fuse is intact, and the 12V switch is on. | DIY Safe |
N/A | The fridge won't run on 230V | The 230V supply is disconnected, its fuse has blown, or the thermostat is switched off. | Check the 230V supply reaches the fridge, its fuse is intact, and the thermostat isn't switched off. | DIY Safe |
N/A | The fridge isn't getting cold enough | Blocked ventilation (including a winter cover left on), a frosted-up evaporator, an incorrect temperature setting, incorrect gas pressure, too high an ambient temperature, too much food loaded at once, the door not shutting properly, or more than one power source being used at the same time. | Check the ventilation passages are clear, check the evaporator for frost, check the temperature control setting, check the gas pressure regulator at the gas bottle, let warm food cool before loading it in, check the door is closing properly, and make sure only one power source is selected at a time. Call a service engineer if the problem continues - never open the sealed cooling system yourself, since it holds corrosive chemicals under high pressure. | DIY Check / Tech Fallback |
Frequently Asked Questions
Q: What does the SN climate class on my Dometic RM fridge mean?
Climate class SN (which Dometic calls 'Extended Temperate') means the fridge is designed to work reliably when the air temperature is from +10°C up to +32°C (taken at the bottom vent grille, outside the vehicle).
Q: How well does an absorption fridge cool in hot weather?
In a hot summer the outside temperature often reaches about 32°C - the top of the fridge's rated range - and once it climbs higher, the temperature inside the fridge will inevitably rise. An absorption fridge needs a heat source to move its refrigerant around the cooling unit (which is why it can run on 12V, 230V or gas), so it has to get rid of the heat from its power source as well as the heat drawn out of the food compartment.
To help it in hot weather: park where the fridge vents get as much shade as possible during the day; unclip the outside vent grilles to improve airflow; and if you regularly travel somewhere hot, consider having a ventilator kit (a fan fitted behind the fridge) installed to boost the airflow - Dometic lists these among its accessories.
Q: What can replace my old Dometic RM fridge?
Dometic's 2023 'New for old - simply swap' guide covers both its absorption and compressor fridges, showing which current models replace older ones. It's available from the catalogues section of Dometic's website.
Q: My fridge won't work on mains (AC) power - what should I check?
Check the fuse in the mains supply and replace it if it has blown, and make sure the vehicle is actually plugged into a mains supply. If both are fine, the AC heating element may have failed - that needs an authorised Dometic service centre.
Q: My fridge won't work on 12V (DC) - what should I check?
Possible causes, and what to do: the vehicle's own fuse has blown - replace it (see the vehicle's handbook); the vehicle battery is flat - test it and recharge it; the ignition is off - switch it on. If the fuse in the fridge's DC cable has blown (the fuse on the relay) or the DC heating element has failed, contact an authorised Dometic service centre.
Q: My fridge won't work on gas - what should I check?
Check the gas cylinder isn't empty (change it if it is) and that the gas valve is turned on. If air has got into the gas pipe, turn the fridge off and on again, repeating this three or four times if needed; if a gas hob or cooker is fitted, switch that on, then try the fridge again if needed.
Q: Why is my fridge running on gas in automatic mode when I'm plugged into mains?
The mains voltage is too low. The fridge switches back to mains by itself once the supply voltage recovers.
Q: Why isn't my fridge getting cold enough?
Work through the likely causes: the cooling unit isn't getting enough air - make sure the outside vent grilles aren't blocked; the evaporator has iced up - check the door shuts properly and the seal is seated and undamaged, then defrost the fridge; the temperature setting is too warm - turn it to a colder setting; it's very hot outside - take the vent grille off for a while so hot air can escape faster; too much food, or too much warm food, went in at once - take some out, and let warm food cool before putting it back; the fridge was only switched on recently - give it four to five hours, then recheck the temperature.