Truma Water Heater: “W17H”
warning RV water heater fault codes
What it means
Hot-water mode was selected while the water heater (boiler) is empty. The unit reports the empty-tank condition rather than heating a dry boiler.
Most likely causes
- Water system not filled / fresh-water tank empty or pump off most likely
- Boiler was drained (e.g. winterized via the FrostControl/safety-drain valve) and not refilled common
- Safety/drain valve open so the boiler will not hold water less common
Safe checks you can do yourself
- Switch the system off and let it cool
- Confirm the fresh-water tank has water and the water pump is switched on
- Make sure the FrostControl/safety-drain valve is in the closed (operating) position
- Open a hot tap until water flows steadily so the boiler fills, then restart in water/hot-water mode
How to reset / clear W17H
- Turn the unit off, fill the boiler with water, then turn it back on — the warning normally clears once the boiler is full
- On CP plus, if the code remains, press and hold / double-click the displayed code and back out to acknowledge it
When to call a technician
If the boiler is confirmed full and the empty-water warning still appears, the water/temperature sensor or valve may be faulty — contact Truma service.
Applies to
Combi 4 · Combi 6 · Combi 4 E · Combi 6 E · Combi Eco Plus · Combi Comfort Plus
FAQ
What does Truma Water Heater code "W17H" mean?
Hot-water mode was selected while the water heater (boiler) is empty. The unit reports the empty-tank condition rather than heating a dry boiler.
How do I reset Truma Water Heater W17H?
Turn the unit off, fill the boiler with water, then turn it back on — the warning normally clears once the boiler is full On CP plus, if the code remains, press and hold / double-click the displayed code and back out to acknowledge it
What is the most common cause of W17H on a Truma Water Heater?
The most likely cause is water system not filled / fresh-water tank empty or pump off.
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Sources
- Tech Tip: Truma Combi Error Codes — Truma Combi error code reference, W17H (Truma (official US site))
Note: Confirmed on the official Truma US tech-tip page; exact display wording paraphrased.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.