Have just replaced the diaphram on my boiler (thanks to Iain for instructions). Now only one problem to solve. After drawing water, the boiler click off but after about a minute it will click back on (humming with no lights on)....the temp lights will click on and the boiler will click into c/h mode (rads will heat up even in hot water mode only)....this will continue for about 5 mins.....it will then click back to humming mode and then switch off completely. Have now noticed that if i switch the c/h on manually, the boiler will operate as normal but the pilot light will not come on..........any thoughts?? - thanks

m@tt, June 2008

took the time to post a simple fault mm but not mention what it is.
why didnt you say i think its ...... however get a rgi to carry out repair so the appliance can be checked properly....TIT!

iain, June 2008

pay for an engineer. you should not be touching boilers if your not corgi registered. A good engineer will fix it straight away its a simple fault.

mm, June 2008

try it! only a few pennies so def worth trying ch sensor. not sure if it works in conjunction with frost protection so maybe worth a punt.

still could be pointing to pcb all confused but maybe worth a shot,

keep us posted

iain, June 2008

Iain....one last question. Could it be either hot water or c/h temp sensor??...forgot to mention that about 4-6 weeks ago the 'radiator with a strike though' warning light came on a few times. If one of those has gone, would it result in these symptoms....?? (cheers Iain)

m@tt, June 2008

the 2mins must be the pump overrun after demand but where the hell is the live supply coming from to tell it to ignite??????? bizarre

could be a mad pcb problem or a number of things but not sure to be honest, would like to observe and listen before making a personal 'ahem' educated guess :-)

someone will have had the exact problem and experience but its whether they arrive here and try to help someone else while they post their problem??????

hope you get it sorted, post back new post with what it was when you do, then at least i'll know for future.

iain, June 2008

Iain....the pin seems to be working ok. Have just switched the c/h on and it does seem to work ok (pilot light is all good). What i don't understand is that after drawing hot water (hot tap off) the boilder will click off, but then click on and fire up c/h for about 2 mins....then back to humming mode and then click off.....strange :)

m@tt, June 2008

dhw demand requires both switches made
ch requires top switch made

im guessing top switch (pump proven) switch is staying constantly made therefore when you stop demanding hot water the boiler thinks its now in central heating mode and fires up again

the only thing that has me a bit baffled is the last part of your message above about manual demand

iain, June 2008

what is the pump proven pin doing? you know the part you just replaced, not that one :-) but the one on top facing up.

when there is no demand, pin should be only visible tip or nothing if it is visible is it stuck keeping microswitch made??????

iain, June 2008