ford ka (not A/C) will only blow hot air!! plz help

[lukeg]

i have checked the obvious like the water levels, the thermostat and have even changed the heater control valve (hcv) after reading previous posts on this site and others!! i am getting 12 volts at the hcv solenoid plug but this does not alter when some one in the car is moving the heat control dial/switch from hot thru' to cold. should it change if so would i pick it up on my meter at the plug end, if it should i suppose its the heater control switch!! secondly is there a door in the heater box that diverts the air to travel over the heater matrix or to bypass it depending on the setting, maybe this is stuck with the air passing over the marix?? or is the selection all done by this control valve that should be on, off or pulse.
im not to good at writing these things so sorry if its confusing but basically im asking if the fault lies in the heater control switch/panel or this door in the heater box (if there is one.)
thank u for your patience any help would be deeply appreciated as i dont want to take the dash out for a closer look if i dont have to. just done the heater matrix in my VW corrado not the nicest of jobs...

[tigger1]

There's a thread on this somewhere - somebody had the circuit diagram for the Ka, you're on the right lines with the electronically controlled valve though I think!