eurocombi a23 tap high for hot water

[jonwish]

Hi.
I have an Ariston Eurocombi a/23 MFFI that wont produce hot water when I turn on my combi shower + I have to turn my hot tap on full to get hot water or even turn it on and off a few times very fast to get the boiler to kick in. (heating works fine + no weird noises coming from boiler at all).

When I dont try hot water the diverter valve pin is set back but when I turn on hot tap the pin moves out but doesnt touch the micro switch.
Is this a diverter valve issue or a micro switch issue? + if a diverter valve issue can it be fixed (preferable if doable) or does it need replacing (as it is quite expensive) or can I just bend the mico switch a little (probably not the best or safest option).

The hot water tap needs to be on full for the switch to get to the point in the image anything below full on and its only half way between!

Thanks in advance for any advice you could give.

 

[jeff the gasman]

Just a new Dow diaphragm should cure that.

 

[jonwish]

WOW. Thanks for the quick reply. Really appreciate the help

Do you mean the diaphram in round brass bit at the end of the diverter valve?
Are they easy to fit?
Do I need to drain the boiler down?
How do I get to the screws (can I undo the grub screws on the neck of the diverter valve to remove and gain better access + if so do I need new seals?)

 

[jonwish]

All fixed now and working better than it has for 10 years.
The boiler is 15 years old and has only ever needed a pump, secondary heat exchanger and now a dv diaphragm so cant complain at all + only took 10 mins to do and cost £30 for parts.

Thanks for the help. It is very much appreciated.