The car is a '91 CQ 20V with 90k miles. Starting with an empty system, I put 4oz oil and about 500gms of R12. The AC first put out super cold air. The next day, the air is only a little bit cool. The compressor is engaging for 2 seconds every 10 seconds. Do I have a leak or do I just need more freon? Or, you just cant tell? Thanks for the assistance. Chris