What could be the cause of your car air conditioner not to have a good cooling effect is because your car system is low on refrigerant, recharging the system with refrigerant is the only way out that can restore it into normal condition. This can usually be done with a few cans of refrigerant and a simple service hose connection.
A/C RECHARGING PRECAUTIONS
Before recharging your car air conditioner yourself please make sure you wear safety glasses to protect your eyes. Also avoid skin contact with refrigerant. The chilling effect of spilled refrigerant can cause instant frostbite on bare skin or eyes!
WHAT TYPE OF REFRIGERANT?
Next, you need to figure out what type of refrigerant your vehicle requires:
From 1995 to newer passenger cars and light trucks, the correct refrigerant is R134a.
NOTE: Do not use any other type of refrigerant.
most 1994 and older passenger cars and light trucks, the original refrigerant use to be R12. Although R12 is no longer available to do-it-yourself person and is very expensive. When older vehicles with R12 A/C systems need refrigerant, they can be refilled with recycled R12 from other older cars (this requires taking your car to a repair shop for professional service), or with some alternative refrigerant other than R12, or with R134a (which requires certain modifications).
CAUTION: Mixing different types of refrigerants is NOT recommended. Use the same type of refrigerant that is already in the system unless you are converting an older R12 system to R134a or another refrigerant.
LOCATING THE SERVICE FITTINGS
Next, you need to locate the service fittings on the A/C system. There are two: a LOW side fitting and a HIGH side fitting. The LOW side fitting is usually located on the suction hose or line that goes from the accumulator to the compressor. The HIGH side fitting is located on the line that goes from the compressor to the condenser.
On older R12 systems, the LOW and HIGH pressure service fittings are screw-type schrader valves. On newer R134a systems, the LOW and HIGH side service fittings are quick-connect style fittings. The LOW pressure fitting is SMALLER than the HIGH pressure fitting.
AIR CONDITIONING RECHARGE PROCEDURE
1. Connect the recharge service hose and valve to a can of refrigerant.
2. Turn the valve on the service hose to puncture the top of the can.
3. SLOWLY turn the valve back out to release a small amount of refrigerant into the hose. This will blow air out of the hose (which you do not want in your A/C system).
4. Close the valve so no more refrigerant escapes, then quickly connect the other end of the service hose to the LOW pressure service fitting on the A/C system.
CAUTION: DO NOT connect a can of refrigerant to the HIGH side service fitting. The operating pressure inside the A/C system when it is running may exceed the burst strength of the can, causing the can to explode! This should be impossible to do because the service hose for recharging the A/C system will only fit the smaller LOW pressure service fitting. But despite that, you should be aware of the danger.
5. Hold the can UPRIGHT so no refrigerant liquid enters the service hose. You only want VAPOR to be pulled into the A/C system (the compressor may be damaged if it sucks in a big dose of liquid!).