Diesel Heater – Experience Report
Shortly before Christmas 2024, at 0°C, our Truma Combi D4 diesel heater (manufactured 2022) failed for the first time. The error codes E545H, E551H, E560H, and finally E603H indicated an electronic blockage. On January 4th, it completely failed with error E603H.
Meaning of the Error Codes
- E545H – Fuel supply error (e.g., air in the diesel supply, clogged filter, or pump problems).
- E551H – Flame failure or no flame detected (e.g., combustion chamber dirty or glow plug defective).
- E560H – General combustion error (possibly due to poor diesel quality, clogged air intake, or deposits).
- E603H – Electronic blockage of the heater after too many unsuccessful start attempts.
The last error, E603H, was the critical point – the heater had automatically locked itself after repeatedly pumping diesel but failing to achieve clean combustion.
This error typically occurs when the heater has tried to start multiple times but repeatedly fails. The electronics then lock themselves for safety and must be manually reset by Truma Service.
Challenge Over the Holidays
Since all workshops were closed during the holidays, quick help was not in sight. Our motorhome dealer is also not a Truma partner, which could have made the repair more complicated. On recommendation, I contacted the Truma importer SELAM AG in Winterthur.
Diagnosis and Repair Attempts
Fortunately, SELAM AG was reachable again in week 1. The friendly and helpful staff quickly scheduled an appointment for me. Using a diagnostic tool, the error codes were read, and the following measures were taken:
Clear error memory, unlock electronics & test run
Result: Heavy smoke, no flame formation.
Replace electronic board & update to the latest version (update from v1.7 to v2.3)
Result: Smoke again, still no flame.
Complete removal of the heater & replacement of the combustion chamber including glow plug
Reason for the Failure
According to the technician, this is a known problem with this heater. The combustion chamber was heavily sooted and soaked with diesel – caused by the many failed start attempts during which diesel was uncontrollably pumped without clean combustion occurring.
This ultimately led to the complete failure.
As a user, one has no influence on this, as the heater's control system regulates this automatically. Cleaning would be extremely time-consuming or almost impossible, which is why a complete replacement of the combustion chamber is the most efficient solution.
Long Waiting Time Due to Supply Shortages
Unfortunately, no spare parts were available, so we had to wait a full four weeks for the repair.
Spare Part No.
34020-01342 Electronics Combi D4 / 4E from 2022 (link)
34020-01336 Burner Combi D complete from 2022 (link)
Mfg. No.
CBD04EU-F-33340024
Costs & Warranty
Since the heater was still within the statutory warranty period, we incurred no costs. Outside of warranty, such a repair would cost approximately 1,100 to 1,600 CHF.
Conclusion
The quick and competent service from SELAM AG helped us greatly, even though the waiting time for spare parts was frustrating. Anyone who owns a Truma Combi D4 should be aware that such problems can occur – and that spare part availability can be crucial.