Truma Combi error codes and water-container limits
Truma Combi codes must be matched to the installed model and control generation. Record the complete display before resetting. The North American chart discussed here covers eco, comfort and the listed plus variants; it is not a universal Combi 4/6 or European-control code table.
Read the matching chart
The Combi troubleshooting chart lists several possible causes for some codes. A code can identify a group of checks rather than one part to replace.
| Code | Condition or branch |
|---|---|
| 17 | Hot-water mode with empty water container |
| 18 | Warm-air outlet or return intake blocked |
| 21 /41 | Sensor/cable or electronics branch; service |
| 24 /44 | Undervoltage below 10.4 V /10.0 V |
| 43 | Overvoltage above 16.4 V |
| 45 | Plus models: missing 120 VAC or overheating protection |
| 112,121,202,211 | Gas supply/shutoff or overheating branch |
| 122,212 | Combustion/exhaust, gas regulation, overheating or electronics branch |
| 255 | Missing 12 VDC or control-panel connection fault |
Do not turn a code threshold into a battery target
The voltage figures belong to this control’s fault interpretation. They do not describe a desirable battery discharge state or prove that the battery alone caused a low-supply indication. Cable, connection and charger behavior may also need testing.
Record accessible indications and whether other equipment is affected. Leave live terminal measurements and gas-pressure adjustment to equipped service. Do not bypass an overheating or airflow safety function.
The water container has separate pressure limits
The Combi operating instructions describe a ten-liter container and a 40.6 psi inlet limit. The pressure-relief/drain setting is different and is not permission to supply water at that higher setting. Keep the discharge unobstructed.
Do not operate a hot relief/drain valve or add water through an improvised procedure. Follow the matching cooling, filling and draining instructions. A tank that can retain water still needs the proper energy and control state for heating.
Storage needs the actual draining procedure
The cited instructions require draining when the unused RV faces frost and state that the furnace has no frost protection of its own. Do not equate a winter-capable RV label with an undrained appliance being protected. Confirm all relevant supply and storage conditions.
For an unknown heater, use hot-water observations; for a separate forced-air furnace, use furnace fault checks. A gas odor or CO alarm requires leaving danger before any reset.