Combi boiler hot water problem

[stantheman100]

My combi works fine on heating but not on hot water. what happens is this: when tap is open right up (fully) it fires, but when open a little or normal amount it doesn't. After searching it sounds like a diverter valve problem, not hitting the switch, but other posts have suggested measuring the flow rate from a tap. What does this prove?

Thanks for any help available

 

[StevenJames125]

sounds like a flow switch/diverter valve problem (depends what boiler it is) - that only makes contact with the switch when opened fully / more flow etc

 

[kevplumb]

(depends what boiler it is)

come on OP starter for 10

 

[MANDATE]

I think you'll find it's all about the diaphram being kept in equilibrium, until you release the pressure on one side by opening the hot tap.
If you have a hole in the diaphram water passes through it when you open the hot tap and reduces the pressure on the high pressure side.
This results in limited movement.
With a small hole, opening the tap fully might just make the micro switch whereas with a larger hole there's insufficient pressure to move valve over enough.