Diesel

Dont know if there are any AirCon experts here, but as the guy I recently took my Ranger Rover to in order to fix the aircon said 'I dont do electrical mate' I was having a go myself this weekend after sourcing the circuit diagrams. Didnt get very far though Here's my post to the RR list -
{green welly mode on}

In my continuing quest to fix my 1996 4.6 HSE air con, I have by now established there are no leaks and that it is full of gas. Also the compressor and clutch work and it can chill the air...

Now when the engine is stone cold a compressor clutch voltage of 9.2 volts seems enough to make the clutch engage and the compressor turn; however it releases once things warm up slightly, giving up until the engine is stone cold again. Connecting the clutch ‘demand’ positive straight to the nearby battery always provides immediate clutch lock up...

So to help me isolate the fault any guidance on the below will be most welcome –

Is 9.2v a reliable acceptable voltage to operate the clutch?

A) If not what is likely to be dirty/high resistance to cause the low voltage?
B) If it is how much is a new clutch!

Why does system still demand clutch to engage with the 9.2v still present when the Air Con is switched OFF on the interior control – MOST curious!

What is the ‘thing’ that the negative supply to the clutch passes through in series. It is located at the back of the compressor – is it a capacitor to minimise spikes when clutch engages/disengages; not on the circuit diag at all...

Finally if I need to replace a sensor (the trinary or high press switch) any time in the future, does this mean a de-pressurisation & re-gas?

Thanks for any pointers!

{green welly mode off}