potterton puma 100e boiler not firing. flow switch appears to be working cos can see it moving and its pushing switch on. has been making hissing noise when you put hot tap on for few secs then ok (since it was "serviced " nearly 2 yrs ago.) ive been told diverter valve buggered. or the fault finder indicates it may be air pressure valve, any ideas???? steve.
boiler not firing on heat or water. pump runs when heat switched on, fan not running, im assuming you mean the extractor fan located at top of boiler, air pressure switch near top on side cant hear anything.