Fault codes / Truma Combi / W 18 H
Truma Combi code W 18 H
What it means: Warm air outlet or circulated air intake blocked.
What to check
Open every duct outlet, clear the return air intake, check for a crushed duct under a slide or behind cargo.
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 E 18 H Circulated air intake blocked, unit stopped
- 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.