I decided to replace the diverter and did the DHW heat exchanger at the same time for good measure. And lo and behold I now have heating!
So the old diverter valve must have got stuck in the hot water position.
Hopefully this will be a bit of useful info for anyone who gets similar symptoms.
At least my prompt elicited a response :) - thanks for replying!
No, the boiler doesn't fire when the heating is called; it just ignores it and the amber light just carries on it's 5 second blinking.
I've had a look at the diagnostic flow-chart in the manual, and the symptoms I've got aren't...
Looks like nobody has any clues.
I'm beginning to wonder whether it is the diverter that's stuck in the hot-water position? I've not read anyone experience this issue with this boiler online, but seen it mentioned with other boilers.
I've got an Alpha CB28 boiler and it has been playing up over recent weeks.
The first problem that it would cut out giving a red flashing light error. I'd reset it, and it would work fine for a while, providing hot water. I've not really worked out when or what causes it to trip over, as the...