Truma · Truma Combi furnace and water-heater systems
W 17 HHot-water mode with an empty water container
The Combi was placed in hot-water mode without water in its internal container.
What it means
Plain-English answer
Truma identifies W 17 H when hot-water operation is selected while the water container is empty. The unit must cool fully before the container is filled and operation resumes.
Owner-safe checks
What to check first
- 01
Turn the Truma Combi off and allow it to cool completely.
- 02
Confirm the RV fresh-water supply is available and the drain valve is closed.
- 03
Fill the water container according to the Truma operating manual, then restart the system.
Safety boundary
Stop and call a technician when
- Do not add water while the appliance is still hot.
- Arrange service if the warning returns with a confirmed full container.
Primary reference
Check the exact manual
Applicability: Truma Combi furnace and water-heater systems. The data plate and specification letter determine which procedure is correct.
Open Truma Combi error-code tech tip ↗Source reviewed August 2026