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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
