Hi i have got a Vaillant VCW GB 242EH boiler about 10 year old it's been brilliant but recently just today for no reason the CH has stopped working, when i had the hot water running(it was very hot as normal)but CH switched off i noticed the CH flow pipe was also hot but radiators cold. I turned off the hot water let the fan stop running so it was quiet then turned the CH on, the th'stat down to a low temp then up until it clicked which is the point the CH usualy switches on, but nothing, when i turn the hot water on the pin off the water section moves up ok & turns the servo valve cam to the micro switch, the pump & the fan switches on, the diverter valve moves to the right & the boiler fires up, so i presume the pin,cam & switch etc is all working, i read on a previous post that if the CH flow pipe gets hot with just DHW working that the diverter valve could be at fault but on another post it said the Vaillant boilers didn't use these as much so i could do with a few pointers, my info is basic as i know nothing about any boiler's except what i can see by watching it & the info off this forum, my backround is in a car parts dept. PS not sure about water or gas pressures i wouldn't know where to start however it has just stopped working & has been for the last 10 years so i can't see water/gas pressure to be a fault when the DHW is running the flames are a good height/colour & the water out the cold tap is at a good pressure so i would like to think they are ok. I take it i would be looking at one or more of the following, Diverter valve, water section or servo valve, oh also this system use to lose pressure so i was often topping it up off the cooling loop so any additives that was in the system all them years ago will probably be diluted to the point of it just being water without additive in the system, could this have any bearing on things many thank's sorry for the long post just wanted to get as much in as possible, regard's Stephen.