I have a Potterton Prima C combi boiler, the main burner keeps going on and off. It comes on for about 5 seconds then goes off for about 30 seconds and so on.
We have had the thermostat replaced last year as we were told this was the cause (this did not recitify the problem), we have just had another gas engineer out and he said he thinks it might be the thermostat (didn't work last time)but never came back to replace it. Does anyone really know what is wrong with my boiler. Thanks

Tammy, January 2009

Thanks for that Tim, a good suggestion to let the next engineer know who we call out, who i'm guessing will probably be as confused as the other two.

Tammy, January 2009

sounds like the boiler is not sensing the flame so it may be the flame sensing electrode but tricky to see from here

tim, January 2009