I'm here! I wondered where everyone had gone.
About your a/c, now.
It is probably low on gas, especially at this age. It needs toget the evaporator down to 3/4 deg before it will cycle the compressor. If it doesn't get that low, then it won't cycle. With the old R12 systems you can use the sight glass to see if refrigerant is moving through, usually with a few bubbles at start up and when cycling. It should cycle all the time the a/c button is pushed, regardless of temperature setting. It could be the thermo switch that sits on the evap is broken, but then you'd get cold air for a while, at least until it freezes over, the the airflow will be blocked. With the fridge only, it uses the fridge thermostat to cycle the compressor, but when the a/c is switched on, the control reverts to the evap temp switch. The other area is the changeover valve for the fridge, but as it's clicking then it's probably ok. It may be that it's not allowing gas to the evap, but the computer thinks it is and is waiting for the evap temp to drop.
Wait until a warm day, run the a/c up while looking in the sightglass with a torch. If there's no visible liquid moving through it, then it's low or there's a blockage somewhere. Check to see if the drier's getting cold, as these sometimes block causing the gas to expand (and get cold) there, instead of at the restricting valve in the evap.
You may get away with the magic in a can replacement gasses, but they're a pain in the rear normally, and are at best a (not so) cheap fix that will come back to bite you at some time, and you probably won't have to wait long.
Best is to convert to R134a, spend a little cash to do it properly, then you have a system that can be maintained in the future. You probably also have a leak somewhere, which even if not visible now, will probably show itself fairly quickly.
If you speak to John at Aircare, he can swap the drier over, change the charge ports, change the oil, add some dye, then gas it up and see what happens. Just be aware that at 17 years old, there are leaks just waiting to happen, so further work may be required down the line. I dealt a lot with John a few years back, and assuming he's still going, he's one of the best in the business. He usually does other work in the winter, but give him a call, tell him I sent you, and he'll fix up up without fitting you up.