I have tried to ask this question a few times but now had any response. Is there someone out there who knows someething about this problem. Any ideas welcome.
I have a fan flued Potterton PrimaF 50 boiler. It fires and lights perfectly but from time to time makes a loud clicking (clacking) noise and the gas cuts (visibly) as I can see through the spy hole. It is very temporary and just ignites straight away again. It is almost as if the gas valve is cutting the supply then reopening it. I turned the heat button down to between 4 and 5 but also removed the front panel, vacuumed out dust, grit etc and checked the airtight seal. Seems to have improved quite a lot but still does it occasionally. Any ideas Please.

Bruce, December 2007

Thanks very much CK. I found the problem. A weak solder joint causing sparking and bad contact from the power source. (Neutral wire). Took the ICB out and repaired the solder joint. Works like a charm now.
BW

BW, January 2008

Many thanks CK I will give it a go tomorrow and see what I find.

Bruce, December 2007

loose connection . cold solder joint{loose}.try tapping lightly different places use pencil or equal tool to tap/w. tstat.bi-metal ? been known to do that some. loose power wire or short somewhere? vent fan vibrating safety sw. trying to open? lots of options ....check loose or vibes. got to b it

ck, December 2007