1984 coupe deville
 

Heater and airconditioner starts to work but will shut off and turn back on by itself. Got the car from old lady who died-immaculate condition with original 31k mileage so I know it has to be an age issue and nothing too crazy

My guess is the A/C control unit (dash). It's one of those parts that have to be completely replaced. My father drives a 1999 Buick Park Avenue that only blows one side, and repair guys said the same thing, replace the unit. Expensive? Only if you buy from a dealer.

TS

Climate control
 

The programmer contains temp. sensor components and is constantly trying to keep interior at optimum temp. so it will go on and off by itself depending on the setting you choose. Particularly if you have it on Auto. It will usually decrease or increase gradually. Before throwing parts at it make sure you understand the system.

IIRC when the battery is getting overloaded, it will start shutting down non-vital loads - like AC -and then if battery recovers, will switch them on again. Are you driving at night (with lights on) or is the battery beginning to die?? If so, maybe a new battery is all you need! When it first happened to me I was scared crazy thinking something really expensive was going on! Hope this helps.

Well,its an programming issue so a better option for it is ti take it to a electrician who know well about the Vintage cars and then proper diagnose it,if you can,t know the issue so its a waste of time to struggle to fix it.