Hi folks,
I have this exact problem also, been fighting with the boiler since moving in to the house a month ago.l
We have had Scottish Gas out 4 times, and now they are coming for the 5th tomorrow.
Pressure is at 1.3 bar.
Had them replace the Ignition PCB Board, worked when he was round, now this morning stopped (after installing on 24th Dec).
I can hear the fan start, boiler seems to fire up and there is a surge of hot water on/off, then runs cold.
When power is turned on there is a burner light, its a two stage light, and goes to second stage (bright light) when you hear it initially fire, seems to fire then stop, then the light goes back to the first stage (dull light).
Possible fault with ignitors or flame sensor or electrical grounding?
There is a thermostat on the boiler, set to 5. 6 being the highest.
When running the heating is awesome, radiators scorching hot.
Could it be that the heat exchanger is blocked, as there were what seemed like small volumes of hot water passing through the pipes initially when fired up?
There is only a thermostat on the boiler itself, not in a room in the house.
Could the clock/control box be causing an intermittent fault?
Would a system flush cure it?
Mega frustrating!
Many thanks,
Mark.
P.S - Happy Crimbo!