If your air conditioning unit is overcharged, there are a few things you can do to fix the problem. First, you'll want to check the unit's pressure gauges. If the pressure is above the normal range, you'll need to release some of the refrigerant from the unit. This can be done by opening the unit's valve and releasing the gas into the atmosphere. Be sure to wear gloves and a mask when doing this, as the refrigerant can be harmful to your skin and lungs.
Once you've released some of the refrigerant, you'll need to check the unit's pressure again. If it's still above the normal range, you may need to add more refrigerant to the unit. This can be done by connecting a charging hose to the unit and adding the refrigerant to the system. Be sure to follow the instructions on the can of refrigerant, as adding too much can damage the unit.