Domestic hot water fine. When heating calls for heat, the divertor valve plunger pulls in to the valve very sluggishly and slowly and sometimes doesnt pull in at all. The pump is running fine and the system has been vented. If the plunger is manually assisted the microswith makes and the heating starts up and works fine. Sometimes the plunger sags back and breaks the microswitch which in turn shuts the heating down.
Check that the small diameter pipe just above the pump is not blocked & check the domestic hot water plunger is going back down all the way, as combi boilers are domestic hot water priority. Let me know how you get on..Thanks
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