any advice please. boiler when it does light only stays lit for about 3 or 4 mins they gas goes out. when trying to relight it you can see the spark and some times it relights briefly before going out. i have checked most things. i dont think its the over heat stat as its not reaching anywhere near a hot temp. could it be related to the pressure switch, which works fine when blowing into it gently, but dosnt work from the fan. the fan is working and the pipes are clear. or could it be the gas valve.
