Potteton Gold 28he a reaches temp then goes on/off every ten seconds

[Alphawarm]

Anyone got a clue? My own Pot of Gold 28he a is throwing a curve ball.
Started with with a hot water problem, overheating, so I cleaned the plate heat exchanger. On restart it now reaches temp on both heating and hot water exactly as it should, but upon reaching temp it stops and starts every ten seconds or so. I've replaced both temp sensors, and even the gas valve. Removed and cleaned the plate heat exchanger again, and checked the condense path is clear. Now I'm stumped, and even considering replacing the pcb just to remove it from the equation. Anyone?

 

[Dotty]

Mate, sorry but we need you to submit another 8 meaningful posts then PM your GSR number to gas man or REDSAW.

Can't answer this in open forum, hope you can appreciate why.

When you've your yellow badge up I'll happily reopen this and then move it to the private forum.