ford fiesta heater valve

hello all,
l need help!!!
i have a ford fiesta 1.3 x-reg petrol, manual. l have replaced the heater valve on it but every other day it wont blow out hot only cold then the next day it will fine. it has a 12v supply to it but is it a permanent 12v feed or only when the heater is switched on. l have 12v when blower is switched on but no reading as soon as the engine is started. where does the wire goto from the heater valve?



thanks [/b]

i think these valves are controlled electronically from a module inside the car,are you sure you havnt just got an air lock in the system after changing the valve?

cheers ch427, had another look yesterday morning to see if there was any air still in there, she has not complained yesterday or today that it was cold so must be okay. thanks for your help