My combi boiler is supplying hot water as well as ever; I don't have any CH. It was serviced last September without any problems.
The boiler tries to light up and stops going through its sequence after about 20secs.
Any ideas what the problem is? All suggestions welcome

chrisrogers, March 2008

I had this a number of times - it was the 3-way valve (part number 235838) sticking. I cleaned it and lubricated a few times which worked for a short period but eventually replaced it when it stuck every few days. Since replacing it,about 18 months ago, the fault has not occurred since.

Duncan Clarke, June 2008

it may be the diverter valve.
you could try to tap the pressure switch, they do have a tendancy to stick. if not sure where it's located just look in service manual. sometimes it works.

gary, March 2008