Baxi 105he instant

[lessthanzero]

Hi just wondering if there is any baxi experts out there. I've had a real head scratcher with this boiler (105he instant) even the manufacturer's technical says there isn't anything more to check or change!
Here goes. Heating- fine ,pre heat function- Fine. no hot water. diverter valve is fine because the boiler rest in hot water mode and moves across for heating, which works.
open tap and the spindle doesn't move. The boiler will fire if you activate the microswitch so I'm thinking easy, diaphram. well it's not the diaphram, sensing tubes or where they lead too. the venturi, filters all cleaned out,and also the cold water inlet filter(easy 15ltr passing through). had a new pressure differential unit(the full part, diaphram assembly and rear unit that allows the pre-heat) put in and the spindle still doesnt move. technical says i've done everything i could do. So i'm thinking somewhere there must be a blockage on a pipe, any help would be appreciated

 

[Baxmax]

Have you got the sensing tubes the correct way around ?

Have you any mixer taps or a mixer shower if so check that any of these items are not "mixing hot and cold supplies" when they should not be ie when turned off,if you can isolate any to prove it would be helpfull

 

[rojaca]

piped up back to front?

 

[lessthanzero]

They are kinda moulded into shape that they wouldn't fit the wrong way around without bending and forcing them.

 

[Baxmax]

In light of last post is it a new install ?

 

[Baxmax]

And the mixers/new install ??

 

[lessthanzero]

No,4 years old. The thing is the diaphragm housing and sensing tube ect were covered in limescale and everything has been cleaned, i just think there must be a pipe blocked not allowing the pressure differential to move, maybe the bypass pipes, they connect onto the back of the diff.
Grassping at straws i know.

 

[onlyfitidealboilers]

I had one the same about half hour ago, pin does not come out when drawing hot water, when i pushed the micro switch all fired up but went heat went around the rads... so me thinks the pressure diff valve is fooked?

 

[lessthanzero]

Cheers for the reply, but it has a brand new complete differential unit on it!