Faulty Biasi Boiler doing head in!!!!!

[Paulgreen700]

I have a Biasi M90E 24S boiler. It has intermitant faults as hot water sometimes works ok but sometimes not at all, and when I put on heating it sometimes works fine for about an hour then stops but you can still hear the pump going and the light flashes faster. If I try turning on and off nothing happens apart from you can hear the pump but if I leave it for about an hour till everything is flat cold it will do the same cycle again.
I have had an engineer out and it decided to work fine for nearly 2 hours whilst he checked it then decided to revert back to its faulty status once he left. He checked the temperature sensors and said the system may need cleaning so I have drained the system and flushed it with water and to be honest it did not look bad at all so now I have refilled it and put some cleaner in to try flush it all out. I also have a radiator in the loft which doesnt get hot anymore even though I have bled it. The boiler is directly below it in my bathroom and I can feel the pipe going up is starting to get hot but obviously its not circulating back. I have even bled the rad whist turning off the supply to either side as i thought there may be a blockage gut water flows either way fine. He said he also replaced the diaphram when he looked at before. Please help as I have 2 small children and it's driving me bonkers.(the boiler is approx 6 years old)

 

[ollski]

The flashing light is a lockout error. In reality the only way to diagnose what is causing the fault is for your engineer to see the fault lights on the pcb when it locks out otherwise it's just chasing shadows.