1: requires diaphragm service kit, you get diaphragm, nut, washer and little o-ring.
Can replace whole lot in ten minutes.
>turn boiler power supply off at fused spur
>under boiler there is a service tap (isolation valve) on your cold supply to boiler, turn it off.
>open hot water tap and leave open. it should stop pretty much instantly
>drop panel down on boiler, unscrew posi screw to release microswitch and put out the way.
> undo impulse tube nut on front half of brass section where your problem is. (leave back tube you'll only need the front off
>pull tube up gently to let air in and should get bit more water from hot tap
>unscrew the flat drive screws on front section.
>keep pressure on section with palm of your hand as you release the last 2 screws and carefully remove section, beware section is under compressed spring hence keeping pressure on it.
>change main nut on front of section
>replace diaphragm
>clean/scrape pin of any scale
>pop little o-ring on pin
>rebuild in reverse.
>when all rebuilt and nipped up slowly turn cold to boiler on with hot tap still open and no power to boiler. when happy no leaks etc then turn off tap, all ok re-instate power.
2: is something i would like to observe rather than guess, switching off while in demand could be temp sensor or scaled exchanger but firing up when not demanded ie after you've turned tap off could be problem with diaphragm mentioned in 1 keeping circuit closed but like i say i would like to observe for 2
iain, June 2008
