Glow worm boiler keeps igniting.

[sootylum]

I've a Betacom 30 boiler fitted a few months ago. Hot water is fine but now that we are using the heating the boiler is playing up. It lights no problem and burns for about 5 min then the burner cuts out but it sounds like the fan is still going. I have to switch it off and on at the mains then it runs ok until it reaches the temp asked for, the burner turns off then after about 15seconds comes on again and burns for 5seconds then goes off. It keeps doing this, any ideas as to what may be causing this.
The guy that fitted the boiler doesnt want to know.

Thanks

 

[fitz1]

ring glow worm direct and ask for a service call under the guarantee.