I have changed the hcv and the control panel , the hcv is pulsing when heater is halfway , and if i leave the 2pin plug off the hcv i still dont get hot air , when the plug is left off this leaves the valve open so hot water should be passing through the valve , all pipes are hot up to the valve , although the bottom hose doesnt get as hot as the top hose , ive flushed and reverse flushed the the heater matrix but i am still not getting hot air out of the heater