C & M calydra comfort 100 no heating

[username taken]

hi all.got called out to a calydra comfort 100 combi the other day.no DHW or heating.a few lights on the dash were flashing and in the MI's it was saying PCB fault.so i changed this with no difficulty.flicked the isolater and the DHW worked a treat.but no central heating.a day later the pump was making a screaming noise so i put this down to bearings.changed that and all is good but still no heating.it is going through the by-pass so i know its getting heated properly as the pipes are red hot but the actual flow pipe off the three way valve is cold.iv give it a gentle tap as iv been to a few where the pin has stuck but no good.im 99% sure its the three way valve but iv not worked on these boilers before so just wondered if anyone had any advice?are they a common fault on these etc?also iv been told its around 8 years old if that helps.thanks in advance

 

[Gary71]

Are you sure the clorifier is reaching temperture as the hot water could be running of the plate heat exchanger, that boiler is hot water priority and will not give you heating untill the clorifier thermister is satisfied, the same fault can be caused by defective thirmister, blocked coil or defective diverter valve.