Smelly Truma Combi heaters

[Guest Derek Uzzell]

Got involved in a discussion on Truma's NEC stand when the owners of a privately-purchased 1999 S-Class Hymer complained that their Truma Combi heater (almost certainly a C6002 model) produced a sickening 'melting plastic' smell when heating water via gas. I reckon most Combis can get a bit smelly towards the end of the gas water-heating phase, as there's no airflow through a Combi's internals during this process and conduction passes interior heat to external plastic components. But apparently this was something else, with the Hymer owners saying doors and windows had to be flung open to disperse the hideous pong. The Truma representative explained that the company recognised that (in the late 1990s) there had been a problem with the plastic material employed for the duct that carries the Combi's blown-air fan and this material's reaction to conducted heat was almost certainly the cause of the smell. Later and current Combi's used a different plastic that was far more heat resistant and didn't smell (Hmmm...!) It was agreed that, if the offending duct could be removed from the vehicle, a free replacement would be provided as a goodwill gesture. Fortunately the motorhome owner lived close to Truma's UK HQ and was capable of carrying out the removal task. The Hymer owner said he had contacted the vendor who had claimed unawareness of the smell problem, saying that the Combi's water-heating mode had rarely been used as the vehicle had spent its life on campsites. In an effort to cure the problem, the heater's insulated top had already been replaced and, on removal, the original top had displayed clear evidence of overheating. I asked if the heater was in the wardrobe base and what ventilation there was. The answer was yes and not much - in fact the present owner had cut an extra ventilation hole into the vehicle's 'garage' to help matters. He wondered how Hymer could justify asking close to £100K for a motorhome where the heating system's installation clearly ignored the heater manufacturer's recommendations. A very fair question, I thought, but few (if any) motorhome builders do a really thoughtful, efficient job of installing a Combi. The Truma technician told me one converter (I forget which) had used inadequately sized screws to attach the heater to the floor. This had resulted in a Combi shaking loose during travel, fracturing the gas connection. I don't know how many 'smelly' plastic blown-air fan ducts were fitted before the material's specification was altered, or how many ducts were replaced under warranty. But if the Combi heater on your 5-or-so years old 'van produces a nasty smell when heating water on gas then a duff duct is probably to blame.

[Guest Pat P]

And there were we blaming the dog!!!!!

[Guest Mike hol]

We are experiencing this problem, amongst others, with the truma on our 2005 Knaus.It is booked in for an investigation with a truma approved agent, next week.