I just bought a 3 year old house, which is still covered by homebond. There is a mechanical valve in the hotpress that controls whether I get central heating or just hot water. The valve, or switch or circuit, is broken - I mean, I can't have hot water only.
Is this something that I can call the developer to fix?
Homebond only covers serious structural faults that the builder will not put right. A broken valve is unlikely to concern them. Call the developer but I wouldn't bother calling Homebond. But to be honest a valve malfunctioning after three years is unlikely to worry the builder either and you probably just have to sort the repair out yourself.
A mechanical/ electrical device such as a motorised valve will only be covered by a 12 month manufacturer's warranty so don't waste your time trying to get the original builder/ plumber to look at it.