worcester greenstar 24i junior no hot water but heating is f

[bunkerman]

Hi. We have a worcester greenstar 24i junior. The central heating is working fine but there is no hot water. If i reset the boiler and then turn on the hot tap while the boiler is doing its initial start up i can trick it into making hot water for a few minutes. if the boiler is on as normal and you turn on the hot tap the diverter valve does not respond. The manual says that if you get heating but not hot water its an electrical problem but the wiring diagrams aren't too helpful. It seems like nothing is telling the boiler to heat the water. Any help would be most appreciated as we're pretty competent and happy to work on the boiler but can't find the info to work from.
Thanks
Stan[/code]

 

[kdoheating]

when u say u reset boiler was the reset light flashing

 

[bunkerman]

Hi. Thanks for the interest. I just press and hold the reset button so it goes thro its warming up cycle. Before i pressed it the blue light was on as normal and the green flame light was on when needed by the central heatinxg. When i turn on the tap without resetting tge boiler the green flame light doesn't respond at all.

 

[bunkerman]

Hi. We have done what others on the forum suggested in past threads and taken out the flow turbine and regulator to check it and they seemed fine. When we reset the boiler the diverter valve does move so we're assuming its not that. Is there a way to check if the turbine actually works without buying abd fitting a new one? Also any ideas what the next thing to check is?

 

[Agile]

It would usually be the flow turbine.

To check them properly you need to look at the output with an oscilloscope.

It could also be the PCB not interpreting the signal from the turbine.

The turbines rarely fail but dont always turn. Sometimes you can blow through them and get enough of a signal. Sometimes a vac will suck hard enough to operate them.

I expect the boiler is providing a DHE preheat and you are initially catching it during this time and so it never reaches the turn off temperature.

Tony

 

[kevplumb]

whhaa whhaa
this is a DIY forum
so who has acess to a scope
oh yeah i have
plank

 

[bunkerman]

Hi. Thanks tony. I don't have an osciloscope (or know what one is!) do i take it then that theres no point disconecting the electrics and putting a volt meter across them with the water running to see if it sends any signal? If it is the pcb i can change this but have noticed others have mentioned cleaning out or replacing the heat exchanger and wondered if this is likely to be the prob before buying a new pcb. I'm a bit worried i'll end up with loads of expensive new parts and a boiler that still doesn't work! Thanks alethea