Truma 4e Combi Boiler

[John Finnan]

Truma 4e Combi Boiler in Caravan with Timer ZUCB control panel. To switch on I press the on button and came on red with control panel not lighting up so giving no indication of a fault so how can you check if there is a fault on start up.

[Geeco]

My Truma boiler (not a Combi) is powered by mains power or gas. If set to gas and the boiler fails to ignite it shows as a red light. If it ignites it shows up as a green light. So if it shows a red light then I suspect it is showing that it has not ignited. If the boiler has not been run on gas for a while it may take several goes to achieve ignition. Have you removed the external cover on the exhaust on the outside of the caravan? It will not work if that cover is on. Cheers,

[Derek Uzzell]

Truma"Combi" combination air/water heaters have no external cover for their intake/exhaust cowl. (I believe only Truma "Ultrastore" water boilers have a removable intake/exhaust external cover.)

I have no practical experience of the (now superseded) ZUCB timer control-panel, but the Combi unit itself does have a 'flash code' error diagnostic function. This is mentioned here

https://serviceblog.truma.com/en/2021/08/10/mover-and-combi-flashing-codes/

and there's a 2010 listing of Combi 4E/6E flash codes here

https://www.dometicrvcentre.com.au/documentmanager/item/139

I remember speaking to a Truma representative years ago and being told that the innate complexity of the Combi's design was such that trouble-shooting (by leisure-vehicle dealers or DIY by owners) was far from straightforward and the flash code system gave Truma technicians at least a clue to the cause of a problem when an enquiry was made.

(Hopefully the Combi 4E will have been installed in such a way that the flash code LEDs are accessible/readable without first dismantling half the caravan!)