Diverter valve issue?

[Uncle Nick]

Hi all, my Warmflow boiler is firing up when set on ‘hot water only’ (and no demand), the radiators then get really hot but there’s no hot water.
The actuator on the diverter valve turns and the valve itself isn't seized.
We've had two engineers look at the boiler but despite changing almost everything neither can get it working correctly.
I appreciate a diagnosis is near impossible without seeing it but any suggestions on what to try next?
Many thanks.

 

[Deleted member 120897]

Is this diverter inside the boiler? Can you isolate the flow valve underneath, then try the hot water?

 

[Uncle Nick]

Is this diverter inside the boiler? Can you isolate the flow valve underneath, then try the hot water?

Thanks for the reply.
Yes it’s an external self contained boiler.
Is that the valve I’ve arrowed?

 

[Deleted member 120897]

Right, what I’ve suggested won’t work - that’s a 3 port mid position valve. So it’s either a wiring fault, or the valve/actuator head. Might have to be one for the oily’s.

 

[Uncle Nick]

Right, what I’ve suggested won’t work - that’s a 3 port mid position valve. So it’s either a wiring fault, or the valve/actuator head. Might have to be one for the oily’s.

Cheers. If I manually open the actuator, it moves to the close position when HW is switched on, the boiler fires but heats the rads, while no hot water.
That’s what made me think the valve may not be physically closing the CH supply.