B5.5 PASSAT FUSE PROBLEM

[Alastair]

Hi all!
i have a 2002 passat tdi 130 with an electrical problem. on friday night past the climatronic unit just turned off without warning and wouldnt come back on. around the same time i got a warning on the dash for an oil sensor which went out again. i inspected the fuses and found a 10 amp mini fuse blown. when i replaced it the climate unit immediately powered up and i thought the problem was sorted. however when i moved the car again the climate unit powered down straight away and again the same fuse had blown and the oil sensor warning reappeared.
i tried the process a few times with the same outcome. when i disconnected the climate unit and put a new fuse in there are no warnings on the dash and the fuse stays intact so i'm pretty sure its not a split wire as the fuse isnt blowing without the climatronic unit connected.
today i tried a climatronic unit from another car and it didnt cure the problem so theres obviously a problem with something else on the same circuit. when the car is stationary and i have the fuse replaced the unit works fine and the fans are working fine. as soon as i move off the climatronic unit powers down again.
please help. i have the car advertised for sale and its holding me back. theres people queueing to view it and i need to find the source as quickly and cheaply as possible so any pointers are very much appreciated.

many thanks