If you notice any of the following signs, you should consider replacing your A/C:
Your A/C is older than 10 years
Poor air flow even at maximum setting
A/C blows hot air due to low refrigerant or duct vent issues
Unpleasant odors resulting from mould or burning electrical components
Loud and noisy when in use
Faulty thermostat
Leaking refrigerant due to a blocked drain line. This is a serious issue that should be repaired promptly because refrigerant is poisonous.