heater problem!

The heater doesn't work at all on the sedici, both of the pipes leading to the heater inside the car are cold!

would i be right in guessing an airlock? the car maintains temperature fine with the fan cutting in when stationary. and it doesn't seem to run cold on roads.

how would i go about sorting it out? where's the bleed screws?

how is it possible to open the bleed screw? it needs a large head screwdriver, but i've only got ones on long handles!! any help would be appreciated!

i think the heater tap may be broken. the mechanism is turning it, but one pipe has pressure in and the other doesn't, but neither is hot. going to try draining the entire system when i get the chance. just in case it is an airlock or such like. got a few more "tests" to carry out on the tap, going to try to see if i can disconnect the plastic bit which connects to the air flap and then see if there's any sort resistance when the tap is turned or if it moves too easily.

I do not think that would be the problem...I had my heater radiator clogged once, I removed it and washed it very well.Now it works
(but be carefull if you mess with it, because it breakes very easy at the in/out pipes)
I hope you'll sort it out
Steve