Vaillant TurboMax VUW: No hot water but CH is working fine

[Freddy38]

My Vaillant TURBOmax stopped working all of the sudden.
No hot water but CH works fine. I'm having to switch the heating on so that I can have a shower!
I located the black wicro-switch and when I press it the boiler starts working & there's hot water when I turn the tap on. The micro-switch doesn't move by itself if I turn the hot water tap on.

What's wrong with my boiler? Is it something I can fix myself?

Thanks very much for you advice.

 

[Freddy38]

It's a Vaillant TURBOmax VUW 242 E (4 green controls on its front panel)

 

[Terry7556]

diverter valve

 

[Andygasman2010]

You can just change the diaphragm. Much easier and cheaper.

 

[The831Bunny]

...or you could employ the services of Gastech in Northampton. Vaillant experts with a huge knowledge.

 

[Freddy38]

Thanks for your replies.
Can I fix it myself?

 

[Terry7556]

you could freddie but an experienced bloke would be quicker by a long way, knows where to get parts quickly and will just be faster every way.plus you happen to be in an area with a lot of bunnymen as already pointed out.
ive changed 4 of these in the last month, each time hopeing its the £ 7 diaphragm. not once has it been the diaphragm, each time i can push the microswitch and it fires like yours, each time the yellow demand light does not come on and each time the bunnymen on here diagnosed the problem and correct solution whether its the casting (the diaphragm sits in here) or the whole valve
freddie listen to the bunnymen