Valliant Turbomax boiler

I have a Valliant turbomax which has developed a strange problem. Over the last couple of weeks while its been hot, I have noticed that during the night, the radiators get hot ? and then back to being off during the day and its not the timer. I'm not sure if the weather has got anything to do with it but I have checked the diaphram in the diverter valve and its OK.
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Anyone ? the boiler is still doing this
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Mayur wrote:

If this was an earler model (VCW or Sine) I would go for the control box but it is not.
I'd like some more info like: Is the boiler firing when the rads get hot? (Likely yes). Is the pump going? (Likely yes). Are the rad getting hot when you draw HW or at other times? Yes diverter valve problem. No is more likely a PCB problem.
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