Worcester greenstar heatslave ii central heating problem

[Dames83]

Hi
I have an oil worcester bosch greenstar heatslave ii combi boiler. It's about 5 years old.
The problem I have is when the thermostat calls for the central heating to come on. Most of the time the boiler light will come on, the boiler might fire up for a couple of seconds then the light will go out and no heating of the rads. On the odd occasion the boiler will fire up for a couple of minutes and I might get some heat into the rads before it shuts off again. I have noticed that if I run the hot water for a couple of minutes, wait for the boiler to finish heating the hot water and then turn the room stat up I can trick the boiler into coming on and heat the rads for half an hour or so before it cuts out.
I had a plumber/heating engineer out today who was a bit baffled by it. He felt it was an intermittent electrical fault, but couldn't offer any further help.
Pressure is good, rads have been bled and it gives plenty of hot water with no issues. New batteries in the wireless room stat.
Any ideas what could be the cause of the problem?

Any help is much appreciated.
Thanks
Damian

 

[ShaunCorbs]

Tbh would need to be in front of it get him to ring Worcester technical while he’s in front of it there a nice bunch

 

[SimonG]

Clock or circuit board. The mkii is a pile of crap.