Weak car A/C can result from something as simple as a clogged filter or as serious as a refrigerant leak. Start with the safe, obvious checks.
Check climate-control settings
Make sure cooling is enabled, the temperature is set low, and the vents and recirculation mode behave as expected.
Cabin filter
If airflow is weak even with the fan on high, a clogged cabin filter is one of the first things to inspect.
Condenser and radiators
Debris on external heat exchangers reduces heat transfer. Cleaning must be done carefully to avoid damaging delicate fins.
Refrigerant should not simply disappear
If the system repeatedly needs refrigerant, there is usually a leak. Recharging every season without diagnosis only hides the problem.
Bottom line
Keep the solution simple: start with the most likely cause, change one factor at a time, and observe the result. That makes it much easier to identify what actually works in your situation.