Hi my 2001 S type 3.0 doesn't blow cold AC until 15-20 minutes after engine starts from cold. I've noticed this in the morning and if I leave the car off for more than 4-5 hours. Once the AC starts blowing cold, its very effective. I checked refrigerant level and also extracted the old refrigerant and re introduced with new oil. Still the problem persists. It's usually not an issue in the morning. But its a damn nuisance if I park it in the sun for several hours and start again. What can be the issue?