OK just to begin...the changing of the air flow under acceleration and hill climbing IS a slight vacuum leak in the system. Try blocking off the heater tap vacuum line as on the VT's the heater tap tends to leak sometimes. Then take it for a run and see if that changes the effect, is so get a new heater tap and fit it about $30 from Repco. If not look for any vacuum leaks elsewhere on the vehicle and don't forget to check for cracks in the vacuum cannister, I think under the front guards.
Right, now to the original problem...... The VT's had the first varible displacement compressor in the Commodores.....it is a piece of **** !!!! You will most likely find that the pressures on the A/c system do not change much and that the vent temp probably will not come under about 16'c. If your A/c tech is any good he should be able to check the pressure readings for you. It is best to check the A/c system with afresh charge of gas because the problem can look just like a low gas situation.
You have three options....1/ do nothing.....2/ replace the compressor or 3/ replace the valve in the compressor.....although I do not recommend this as it is usualy a waste of money because the compressor tends to return to a low pump situation.....oh just to let you know....you can't do this yourself anyway.
There is a replacement mount and compressor kit for the VT (shows you how **** the original is) so ask your A/c tech about them as the cost is very close to the cost of replacing the compressor. Or you can get a rebuilt unit. If your a/c tech knows little about either email me and I will see what I can do for you.
One thing you can check on your own is the heater tap... because other than causing a vacuum leak they tend to leak water paste their internal flap. There should be 4 hoses connected to the heater tap located on the drivers side strut housing. Make sure the knob inside has been in the fully cold position and then check that the two hoses going into the firewall are fairly cold and not hot.
Hope this helps....regards GUY
