Potterton 28i DHW not heating up

[MARTSAM18]

I have no hot DHW through my Potterton 28i boiler, the CH is fine, I've changed the 3 way valve motor to no effect. I've checked A8 on the circuit board 1 & 3 cables (CH) has power 1 & 5 DHW doesn't, does this mean the PCB has gone or the Differential valve. Hope you can help, I'm new to this game, thank you. Sorry if this has been posted before.

[Oliver_murphy]

Its a combi right?

Look at the Divertor valve, you should be able to find a diaphram in there, in what looks like a spaceship/saucer.

Replace the diaphram.

Easy