My boiler appears to cut out after first heating to the target temperature. once the max temp is reached it will ignite and cut out about every 5 seconds. Reseting appears to make no difference. However once the system has been allowed to cool to below 10degC approx it will function correctly again - until it reaches the max. CH seems to work ok although the rads only get warm during the "pulsing" never hot. I am happy it's not the exchangers as the system can generate hot water once the unit has been allowed to cool.

Any ideas?

MSW, January 2009

I'm sorry, it's not an answer but I have the exact same model with exactly the same symptoms! You described them better than I could. I gave up with it altogether yesterday and switched it off and used electric heaters in whichever room I was using. This morning (with snow on the ground) it appears to be working again so I had a quick shower before challenging it to heat the house. I'm concerned that if I call someone out it will appear to be working normally so they won't be able to fix it but will still have to charge a call out fee.

MJB, February 2009