Combi boiler luke warm water but radiators working fine

[jpfrustrated]

Hi, I have a Chafoteaux Maury Britony combi se 80 ... Yes I know ... it came free of charge with the slightly delapidated flat I recently bought and worked fine for the first 3 months.
The heating is working fine but the hot water is now luke warm at best and only fires up the boiler when the taps are fully open. The luke warm water is constant and not fluctuating.
At this point I did the right thing and called in a boiler engineer from a mid sized local company.
He replaced the three way valve, motor and divertor valve cartidge, gave me a thumbs up on the way out the door and a bill for the work. I've paid the bill but it's not solved the problem.
The hot water is now slightly warmer but still only works when taps are fully open.
So I got my tools out.
I did some home work and I've now replaced the plate heat exchanger. tested and for luck changed the thermistors, swopped out the pcb and flushed the central heating system. Still no joy.
I can't afford to have the boiler replaced at the moment, so if anyone can help, it would be very much appreciated.

 

[cross thread]

Follow the cold inlet to a black plastic housing on the front is a knurled round bit it has probably fallen apart and needs replacing it is a easy swap with cold isolated.

 

[cross thread]

61302411 Part number I https://www.ebay.co.uk/itm/29587161...RBAUwhchB6oSCGQwvJ3/sfxaiZ|tkp:Bk9SR4DoqZi-Yw

 

[ianmcd]

DHW FLOW SWITCH

 

[jpfrustrated]

Many thanks. I'll order one up and give it a go.

 

[jpfrustrated]

The dhw flow switch seems to be fine with a multimeter test but yes I can your thought process and I might just change it out anyway as it's a cheap part. Thanks cross thread for the advice, thats the part I'll chuck in next.

 

[jpfrustrated]

Thank you cross thread!!!!!

It took me 2 minutes to fit the part you recomended and now I have hot water again.
The boiler enginer had said that the only option was to replace the boiler at a cost of £2800, I'm so glad that I went with my gut and had a go my self.
If anyone else is having the same issue and wants to check the part, it should have a white plastic rod protruding from the front with an internal spring connected. This had snapped on mine. The part is a "water control" part number 61305290 £40 or less for an original part from ebay.