The symptoms: An older Barlo Duo has the fault that it will work for a while (hours to tens of hours) and then stop with an unlit pilot light. Light the pilot, and it works again, for a while, both heat and DHW. Timer, thermostat etc all work as expected.
From the symptoms, I'd guess at crud in the pilot light jet, causing the fan to sometimes blow the pilot light out on purge. There are two jets to the pilot light flame, one up, one to the right towards the thermocouple, with the one on the right looking a bit weak.
The problem is that it's a mate's unit, I was in for a short visit, and didn't want to start in on it without dire need. He'd just had it serviced, and didn't want to get them back again, feeling that they hadn't proved themselves trustworthy. (I'd have had them back, but I can see his point.)
How does one get at the jet? If it's reasonably easy to get to, I'd forward instructions on opening the unit and giving the jet a scrub and a blowthrough...
Thomas Prufer