Could be low on freon,
You switch the carborator with the ac and then rewire the inside to the dashboard
check your ignition switch
ignition switch or key and tumbler.
It is not the blower motor,it is the speed switch on the dash.This is a common problem in many vehicles.
ignition switch happened on my 94 also that fixed the problem but you have to drop the steering wheel
The ignition switch is bad. Replace it.
you have an AC leak
The blower motor speed switch is burned out or the fuse is blown.
does the ac just stop or does the defrost also come on out of the blue?
Quite a number of problems can cause your AC to fail, but perhaps the most common is low refrigerant. Refrigerant usually leaks, or more accuately seeps, out of the AC system. Over time, you'll need to add more refrigerant. The system detects low levels of refrigerant and shuts off the compressor until you add more.That is NOT the only reason AC systems "stop working".Faulty compressor, clutch, relay, switch, fuse... all of these and more can fail, causing the AC to stop working.
Most likely is a bad ignition switch.