ACC question

[Turboken]

Hi,
I am having some trouble with my ACC on my 02 Aero. I suspected that there was a issue with the system when warm air was comming out of the vents even though the ACC was set to LO so off the car went to get the system regassed. The regassing machine firstly removed 650 units of refridgerant from the system, carried out a cleaning cycle then filled the system with the recomended 750 units along with a UV dye,this told me there were no leaks in the system or the system would be empty after 6 years of operation.

Today when i tried the ACC down at the LO setting everything was great then the air from the vents was getting warmer so i switched off the ACC panel. When i got home i opened the bonnet and removed the grill,started the car and left it running with the ACC on LO for around 15 mins. whilst the car was running i felt both pipes that go through the bulkhead, one was freezing the other only slightly warmer,there was visible flow of refridgerant through the sightglass on the unit behind the grill when the compressor was running.

So after that long explanation here is my question -- has anyone had the same issues with their car , if so what was causing the problem and should the compressor switch on/off (30 - 40 second cycles)or stay on all the time ???