Check battery, connections, etc. The light will come on when the alternator is not charging. May need an alternator and battery being that old. Call Milt's Service Garage to schedule an appt. (707)643-7548
Ac does not always stop but that might be an issue as to why a low charge would cut off ac and then could not get to start again. The problem is related to the extra "recreational sized" battery on the passenger side under the hood. Be careful with the replacement of the battery due to the fact the air lines on the suspension are located under the battery and leakage from installation of a noncompliant battery could cause the lines to be damaged thus dropping the car on the suspension. If this occurs, you will be required to replace the plastic lines with new ones as they cant be spliced due to the amount of pressure.
these cars have two batteries. the main vehicle battery, and a auxiliary battery located on the right side of the vehicle under the hood. I believe the washer tank will have to be removed to gain access to it. It will cause the vehicle to go into what is called energy saver mode (ac will stop working) and the red battery light will come on