Worcester 24CDi DHW problem

[Johninsale]

Hi, can anyone help diagnose this problem please? My daughter has an old Worcester 24CDi. The heating works fine. The problem is with the DHW. The boiler is very close to the boiler. However, the hot water tap has to be turned very nearly fully on before the red light comes on to say that there is demand. It then takes quite a few seconds longer before the boiler fires up and even then the water only gets luke warm. The slightest reduction in flow causes both lights to go out. I am guessing that there is either a faulty flow control sensor or possibly sludge in the heat exchanger. Can anyone confirm if I am on the right track. I have looked at the paperwork we have for the boiler but it isn't much good for fault diagnosis and even worse for parts identification. I would appreciate any pointers guys.
Thanks
John

 

[picasso]

Worn diaphragm would cause the hot water not to start except when you have full flow, check to see if the flow pipe gets hot when you run the hot water, could be a sticking divvy valve.

 

[Johninsale]

Hi, sorry for the delay in getting back to you and thanks for the suggestion. I did as you suggested and replaced the diaphragm and it appears to be working fine. That just got me oodles of brownie points with my daughter.
Thanks again.