worcester 24 cdi luke warm water

[motherearth75]

hi ive got a worcester 24 cdi which gives me hot water when the central heating is on,but when its water only my water is just about luke warm.
Is this the diverter valve or dhw thermister

 

[gas4you]

Could be just the diapragm gone!

if heating is off and hot tap turned on does boiler register that there is a demand for water?

 

[motherearth75]

red light comes on to confirm the hot water tap is open

 

[gas4you]

If heating off and hot tap on does the heating flow pipe to rads under boiler get hot? if so diverter need changing as it is stuck!