If your aircon only works on some fan levels (eg: 3 & 4 only) then you will need to replace your fan speed resistor. They cost about $54 from your local holden dealership. The job only takes 10-20 minutes depending on how confident you are. 1. Pop the bonett 2. Undo the bolts ontop of the wipers, lift wipers off (WD40 may be need as sometimes they are hard to get off, remember to mark where the wipers were because they need to be put back ni the same position otherwise they wont wipe the windscreen smoothly) 3. Undo the black bolts under the wiper arms once they are lifted off. 4. Pull off the rubber seal which is under the bonett (just before the black plastic cover where the wiper arms come out of) 5. Remove the 5 little clips which are along the base of the windscreen (use a small screw driver to lift them up) 6. Lift the black cover up but be careful as they crack easily 7. Undo the 2 screws on the dome which is located towards the centre of the car 8. Under the dome undo the other 2 screws which reveals the fan speed resistor, unplug it and put the new one in (you will notice one of the wires are broken on the old resistor) 9. Do steps 2-8 in reverse. Hope htis helps because it helped me and now mine works. Thanx to several sources for helping me fix this so i tohught i'd type up a simple method to help others.