Baxi 80 Eco DHW or CH Diverter/Manifold Fault, An Odd One

[ChrisChaos]

Right then, I'm Proper Stumped and I don't say that lightly

The CH on this boiler is fine, (a while back it had been leaking a little and losing pressure but I traced that to a small leak from the junction between the primary Heat Ex and left hand Flow Pipe, replaced an o-ring and all's good.

But have had to go back to it as the DHW has now stoped working, turn tap on and the rod from the DHW Pressure Differential Valve Does Not Come Out to push the micro-switch, So no ignition/flame/heat, but plenty of water pressure/high flow rate from 'hot' tap

Obviously the DHW Differential Valve I think, so check diaphram and rods and all is good, Got a rebuild kit for the CH Differential and the Manifold despite no obvious visual faults with old one and still no change

If I Manually trip the front micro-switch, (on the DHW valve) the the Rod on the top of the CH Valve pops up and hits the switch there regardless if the hot tap is running or not

Been through fault finding flow chart and come up with nothing

Any Ideas that don't involve a 16lb sledge hammer anyone ?
ta
Chris

 

[45yearsagasman]

Follow the two differential pipes to the inlet assy and theres a good chance that the fault will be in there. There are very few hydraulic faults mentioned in fault finding charts. If the diaphragm is perfect then you probably have no differential pressures in those pipes.
I would suggest you sign up for the Combustion chamber section if you are Gassafe. Lots of experience on there and its free.