Your air conditioner may be making a loud squealing noise because the AC compressor, which helps cool the air, could be malfunctioning. This could be causing the noise you are hearing.
Possibly a stuck relay
Your compressor has possibly stopped working. If you are lucky, the serviceman will only have to replace the freon to get it going again.
A quiet mode would assuredly slow the fan down, possibly slow the compressor too on higher end units.
Your air conditioner may be running constantly because it is struggling to cool your home efficiently, possibly due to a clogged air filter, low refrigerant levels, or a malfunctioning thermostat. It is important to have a professional inspect and repair your air conditioner to ensure it is working properly and efficiently.
There can be quite a few reasons as to why the compressor is squealing when the a/c is activated. The most common cause is a loose accessory drive belt (or serpentine belt on some vehicles). Another cause is a loose or weak a/c clutch or possibly a faulty or defective compressor. Try tightening or replacing the accessory drive belt/serpentine belt. If that does not work, have compressor checked at a qualified repair facility.
You have a problem . possibly the inside coil needs cleaning. and the air filter is clogged. May even be low freon. How about the cooling? whats happening there.
Possibly a low refrigerant charge
possibly a bad brake...you should get all brakes done
Possibly the compressor is not functioning/engaging or the a/c control is malfunctioning. Fuses and relays may be worth checking as well.
Modern vehicles have what is called an Idle Air Control valve, which is activated when you car is started, as well as when the AC compressor is on in order to compensate for the load the compressor has intoduced to the motor, and to keep the motor from dying as a result. Lifing the RPM's up is normal when the compressor starts, but if it seems erratic or like somethings not acting right, it could possibly be not working correctly too.
Possibly the wrong belt was installed or most likely your belt tensioner is bad.
Several reasons could be causing this issue. It could be due to a dirty air filter restricting airflow, low refrigerant levels, a malfunctioning compressor, or poor insulation in the room causing cool air to escape easily. It's best to have a professional HVAC technician inspect the unit to determine the exact cause.