AC charge after dormant?
 

HI, If I try to recharge my AC after not working for 15 or 20 years or so, will I cause any damage?

You should replace the receiver/dryer with new. I would remove the compressor and drain any oil in it, and replace the oil. Just measure what drained out. It should be 2 or 3 ounces. Then pull a long vacuum. A nitrogen purge would be nice. Replace the oil in the vacuum pump, and pull a one hour plus vacuum. Then add refrigerant to just the low pressure side, slowly and turn on the engine and let the compressor run. Check the pressures on the high and low side and and get them to normal pressures for the air temp.

Don’t waste $ on an over the counter DYI fix-all-one can recharge kit. They’ll work on a pinch for a low pressure side boost but if your leak isn’t found that’s $ down the drain.
If your dryer was mounted in the wheel well, good chance the hose connection corroded.