The answer to 'air conditioner not cooling' is that there are several common causes, including a dirty air filter, refrigerant leaks, issues with the compressor, or problems with the thermostat or electrical components. Symptoms may include the unit running constantly but not cooling effectively, warm air blowing from the vents, or the compressor not turning on.
In many cases, simple DIY troubleshooting and maintenance like replacing the air filter or cleaning the condenser coils can resolve the issue. However, if the problem persists or you suspect a more complex issue like a refrigerant leak or compressor failure, it's best to call in a professional HVAC technician to diagnose and repair the system properly.