The ac pump may be seized up.
If you have the defroster on, the ac comes on automatically.
the ac in the car cools, the fact you have set a higher temperature than the ambient tempereature means that the car's heater is working and so is the ac, if you wish to heat up your car, turn the ac off.
If it has AC assist and the compressor is shot, cut the belt or disconnect the defrost from the compressor.
turn the car on
The AC is taking energy
Why does your ac and heater fan turn off and on
Well you have to press the button that says off to be able to turn it off.
Your mass airflow sensor could be bad or your exaust gas recirculation valve.
Check the alternator or the main lead of the ac wire to check for either if there is too much pressure is being applicated to the alternator or if theirs a shortage in the main lead wire to the ac
The squealing noise from your car's AC when you turn it on could be due to a worn-out or loose drive belt, which may need to be replaced or adjusted by a mechanic.
to turn it off on pleasant days
AC runs on the battery. If the car is off and you run the AC, then start the car, it will stall.