Light comes on: low refrigerant a/c is off.

sounds like restriction, may require a vacuum. i also would check the o-ring that is inside the (i believe the high side pressure line). sometimes those rings go bad and move into line causing that restriction, sometimes leak. i would try that first, something you can do at home. ask a local radiator shop for the name of the item i mentioned for future reference and add it here for my records, if you dont mind of course. if you do system leak check, get the stuff that shows in black light, easier then leak detector (old school). just remember that A/C compressors and systems are made to as a "sealed system", if freaon is low, there is a leak or in your case restricition. check to see if there is any better freon chages that are better then the 134A, that you are compatible with. I sure miss R12, that was the coldest A/C systems around.