Wshat's wrong with my Potterton Netaheat can I get a gas valve ?

This was asked in 2006 and not answered and now I have the same issue. Is there an answer please and if its the gas valve where do I buy one ?

Hi got a potterton netaheat 16/22 & when it starts up a loud click is heard (gas valve?) & it operates normally. Every now & then the loud click which I assume is the gas valve hasd a fit & goes crazy clicking like mad but the boiler does not go out. It can also be started if the boiler casing is banged.

Is it the gas valve or the control panel thats at fault?

(Chris Straw October 2006)