It's usually the fan. They're designed to go wrong one day over the warranty
Rod
November 2011
water keeps dripping from pipe outside.new water presure valve(3BAR)FITTED AND AIRVENTER.this only happens on heating not hot water.after about 1hour presure is down to zero.
c.ellison
November 2011
if its a 30 40B, GC 41 315 81, and its a Robert Shaw valve, you can get one from:-
although it'll cost nearly £300, then find a fitter at a reasonable price, corgi registered of course.
freeze nomore
January 2010
Check power is getting to boiler (Permanent live and thermostat/ programmer). Make sure pump is working. Make sure water is in system (pump not dry). If all these check out it may be the gas valve.