Fault codes / Truma Combi / E 18 H
Truma Combi code E 18 H
What it means: Circulated air intake blocked, unit stopped.
What to check
Clear the intake and the warm air outlets. If it comes back with everything open, the air sensor or electronics are at fault.
Learn the system
Practice it on a service call
Guided diagnosis
Other Truma Combi codes
- Truma Combi code W 17 H Hot water mode selected with an empty tank
- Truma Combi code W 18 H Warm air outlet or circulated air intake blocked
- Truma Combi code E 21 H Room temperature sensor or its cable
- Truma Combi code W 24 H Battery dropping toward cutoff, below 10.4V
- Truma Combi code E 41 H Electronics locked out after repeated overheating
- Truma Combi code E 43 H Overvoltage, above 16.4V
- Truma Combi code E 44 H Undervoltage, below 10.0V
- Truma Combi code W 45 H No 120V to the heating elements, or overheat protection tripped (eco plus and comfort plus)
- Truma Combi code W 255 H No 12V to the Combi, or no connection between the Combi and the panel
- Truma Combi: E 112 H / E 202 H / E 211 H No gas or overheat: cylinder closed, shut-off valve closed, or overheat protection tripped
- Truma Combi code E 212 H Combustion air intake or exhaust blocked, gas valve closed, regulator fault, overheat, or electronics
- Truma Combi: E 121 H / E 122 H Flame lost or unstable during a run
- Truma Combi: E 2 H / E 16 H No flame: gas off, air intake or exhaust blocked
- Truma Combi code W 27 H Circulated air intake or warm air outlet blocked
- Truma Combi code W 29 H Battery below 10.4V
Full field guide: Truma Combi furnace and water heater
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.