Baxi 105E Hot Water Problem

[Syncro]

I've read a good number of threads regarding problems with this boiler but none exactly like this one.
Central heating works fine.
Hot Water Pre Heat works.
Hot Water on demand no go.
I think I've found the problem but not a solution.
I've stripped and cleaned the Pressure Differential Valve, then without the micro switch connected I can see the pin move out when I run the hot water tap, replace the micro switch onto the assembly, run the hot water - nothing.
Remove the switch, run hot water and operate switch manually and presto! it works.
So the push rod it seems isn't traveling far enough to operate the switch.
Any ideas hints nudges etc all much appreciated.

Expansion vessel is buggered but I don't think that would have any effect on hot water on demand.
If I fit a secondary expansion vessel, would I just connect it in a loop from the CH return ?

 

[nogoodatfaultfinding]

If its the pin that pushes the water switch that has gone (Behind the diaphram chassy) unfortunately you need to change the full lot as it is built in, some will tell you that you are able to grease and clean but this usaully (i find) cuases more complications, it is also far faster just to get all new.

On your expansion vessel the answer is a resounding YES it will affect your Hot Water badly that is why you need the 1 bar pressure in the boiler.
Its for your hot water!!!

 

[Syncro]

Thanks for the quick reply.
Do you think THIS will do the job ?

 

[nogoodatfaultfinding]

Yeah easily.

And as you said (and if you have the space) just tap it into the return preferrably just on the pipework that connects under the boiler.
You can use a fittings kit (dearer than the vessel) or turn it down the way just as long as its supported.
And make sure its pressurised and that you can get to the pressure nipple after fitting.

 

[slapper]

If its the pin that pushes the water switch that has gone (Behind the diaphram chassy) unfortunately you need to change the full lot as it is built in, some will tell you that you are able to grease and clean but this usaully (i find) cuases more complications, it is also far faster just to get all new.

On your expansion vessel the answer is a resounding YES it will affect your Hot Water badly that is why you need the 1 bar pressure in the boiler.
Its for your hot water!!!

And hears me thinking it was mains pressure on the sening tubes that operated the pin on DHW,surely if the diaphragm has got a minute hole in it,then it wont push the pin out far enough to operate micro switch. Or am just thick

 

[Syncro]

If its the pin that pushes the water switch that has gone (Behind the diaphram chassy) unfortunately you need to change the full lot as it is built in, some will tell you that you are able to grease and clean but this usaully (i find) cuases more complications, it is also far faster just to get all new.

On your expansion vessel the answer is a resounding YES it will affect your Hot Water badly that is why you need the 1 bar pressure in the boiler.
Its for your hot water!!!

And hears me thinking it was mains pressure on the sening tubes that operated the pin on DHW,surely if the diaphragm has got a minute hole in it,then it wont push the pin out far enough to operate micro switch. Or am just thick

Far from it mate, you're spot on, the diaphragm has a hole in it, near the outside edge about 1/16".
I've done a right bodge temporary fix with bin liner and super glue
Spare ordered and on it's way, thanks to all who replied.