If you purchase a used car and suddenly find that your A/C is not working or not working properly, there are a couple of reasons why. Just like the air conditioning in your house, you need to perform regular maintenance on your car's A/C. The maintenance might have caught a problem in the works, versus the situation you are now experiencing. However, you can still "self-diagnose" the problem, buy the corresponding parts, and then have an auto AC maintenance service put the new parts in your car for you.
Blowing All Hot Air
If you flip on your car's A/C and all you get is hot air, your car's A/C may be entirely out of refrigerant, amongst other things. This is probably the first thing to check before you buy parts and before you have the technician check out the A/C system. Thankfully, you can buy refrigerant and fill it yourself, if you know how.
If the cold air seems to be there, but there just is not any blowing or movement, your compressor may be shot. The compressor is the driving motor that exchanges refrigerant for cooled air between the evaporator and the condenser. When the compressor is dead, the cycle does not occur and the air is not blown into the car.
There may also be a problem with the evaporator. The evaporator converts the gel refrigerant into a gas, which is compressed, condensed, and ejected back into the car as safe-to-breathe, icy cool air. It is easy to check if the evaporator and/or compressor is shot. Just turn on your A/C full blast, pop the hood of your vehicle, and watch for vibrations emanating from either of these components. The evaporator should feel quite cool if it is working, and the compressor will vibrate and feel very warm as it works to compress the gas from the evaporator and send it through the condenser and back to the vents.
Leaks from the Front of the Car
In most vehicles, this is where your condenser for the A/C sits. It is normal for it to "sweat" and drip a little, but if you see a blue or silvery-colored drip and/or it is rather steady, this is not normal. This is actually the refrigerant leaking from the condenser, and a leak of this sort contributes to air conditioning that is barely blowing cold air inside the car. The worse the leak, the warmer the air blows.
For more information and help with your car's A/C, contact a auto service company, like Modern Auto Air.