valiant Turbomax Combi , Flow Divide Valve problem?

[Stopstalking]

Having just moved into a flat, and the boiler needing a new pump, i thought my boiler problems were over with, but no!

up until last week , when the hot water tap was turned on, the boiler kicked in and heated up the water. now it only does this sometimes.
50% of the time the valve activates, and i can see it press the microswitch. the boiler sounds like its about to heat the water, then goes silent, and will not heat it. if i turn the water on and off a few times SOMETIMES it will start.
does this sound like a valve problem, a microswitch problem, or does this switch connect to a controller ( which i was told was replaced before i moved in ) and this has died?
any suggestions as i have been quoted £190 to replace the valve!

james

 

[GasAid]

Sounds like it could be the motor on the diverter valve not driving the valve to the right position; especially if you say that you can see the flow switch engage...

What Vaillant is this on exactly? As diagnosing an unknown model is very difficult especially where I'm sitting