Hi Guys , new to this forum and hoping someone can shed a bit of light on my boiler issue. My glow worm 30xci is playing up . When you run the shower /hot tap it runs fine for about 2 mins then runs cold for about a minute then runs fine again until you turn of the shower . I ve monitored the boiler during this cycle and it comes up as F14 (which is CH flow temp is greater than 95'). I ve read some threads that say it could be the plate to plate hx, or the 3 way valve or motor or even pump or PCB . ( The Pcb was changed in oct 2017 before we bought the house). When at the boiler, the boiler comes on when demand is there and when touching both the CH flow pipe and the HW outlet you get a cold CH flow pipe and and hot HW flow pipe as expected . Then after about 2 minutes the CH flow pipe goes extermely hot very quickly and brings on the F14 fault , Boiler turns off then after about 1 minute fires back up and runs ok. Whist the hot water is running we are also getting the radiators warming up . Have had a gas safe engineer out who did nt get the f14 fault to appear but adjusted some pressures and basically ruled out a blocked HX . He suggested i change the HW thermistor if i had any further problems which i have but to know avail.( weirdly i can t get hold of the same engineer and am still yet to pay him for his initial house visit despite attempts to contact him). I guess my long winded question is what is the more likely failing component in the above situation , HX? Diverter valve ? motor ? or PCB again. There is no abnormal noise when running the hot water so i m assumming flow thru the HW side of the HX is ok , so does this mean the prob could be in CH side of the HX ? . Sorry about the long winded thread but could really do with some major pointers. Cheers look forward to any replies of help/advice or just experiences of the same thing .