Truma Water Heater: “W255H”
warning RV water heater fault codes
What it means
Communication/power warning: the heater is not receiving 12 V DC power, or the CP plus control panel has lost its connection to the heater electronics. A steadily shown W255H usually points to power/wiring; a blinking W255H can also appear after several failed ignition attempts without adequate gas supply, or when the master switch was turned off.
Most likely causes
- Blown or corroded 12 V fuse feeding the heater most likely
- Loose or damaged blue control-panel data cable between CP plus and heater common
- Battery disconnect / master switch turned off so the heater has no 12 V common
- Repeated failed ignition with no/low propane (blinking variant) less common
- Heater electronics fault rare
Safe checks you can do yourself
- Confirm the RV battery/master switch is on and the battery has a healthy charge.
- Check the 12 V fuse that feeds the Truma heater and replace if blown.
- Inspect the control-panel data cable plug at both the CP plus panel and the heater for a loose or backed-out connector.
- Turn the system fully off at the panel, wait about a minute, then power back on to clear a transient warning.
How to reset / clear W255H
- Switch the heater off at the CP plus panel.
- Cycle the 12 V power (master switch off, then on) and ensure the fuse is intact.
- Turn the heater back on at the panel; the code should clear once 12 V and the data link are restored.
When to call a technician
12 V power and the data cable are confirmed good but W255H persists, indicating a control board or harness fault.
Applies to
Truma Combi (Combi 4 / Combi 6 / Combi 4 E / Combi 6 E) · Truma Combi D (diesel) · Truma VarioHeat · CP plus control panel
FAQ
What does Truma Water Heater code "W255H" mean?
Communication/power warning: the heater is not receiving 12 V DC power, or the CP plus control panel has lost its connection to the heater electronics. A steadily shown W255H usually points to power/wiring; a blinking W255H can also appear after several failed ignition attempts without adequate gas supply, or when the master switch was turned off.
How do I reset Truma Water Heater W255H?
Switch the heater off at the CP plus panel. Cycle the 12 V power (master switch off, then on) and ensure the fuse is intact. Turn the heater back on at the panel; the code should clear once 12 V and the data link are restored.
What is the most common cause of W255H on a Truma Water Heater?
The most likely cause is blown or corroded 12 v fuse feeding the heater.
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Sources
- Truma Tech Tip: Common VarioHeat Error Codes — VarioHeat error-code tech tip (W255H) (Truma North America)
- Truma CP plus Operating Instructions — Troubleshooting guide for Combi gas heater (H) — CP plus operating instructions, fault code W255H (Truma (OEM-hosted, Imperial Outdoors))
- W255H in CP plus display or no more symbols in display after reset — Truma service blog, W255H (Truma Service Blog)
Note: Behavior differs slightly between the analog CP classic (shows as no-communication) and digital CP plus (W255H). The blinking-after-failed-ignition behavior is documented in Truma support materials but the steady code is primarily a 12 V/connection fault.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.