In the past few years, many owners have discovered that fixing an inoperative air conditioner can cost a few hundred dollars or more, depending upon the make and model of vehicle. The reason is that the old standby R-12 refrigerant, trade named DuPont Freon, has been replaced by R-134a. Touted as being environmentally safer than its predecessor, R-134a has been standard since ’94.

If your older vehicle needs major repairs to the air conditioning system you can expect to replace refrigerant and the oil in the compressor in addition to the old components. You also may need to install a retrofit conversion. Do not allow anyone to mix refrigerants. They're not inter-changeable. You cannot add R-134a to your older air conditioner without first flushing the system. Further, according to the Car Care Council, some substitutes are volatile mixtures of propane, butane and flammable hydrocarbons. Keep in mind the fact that if your vehicle is leaking refrigerant, you're damaging the ozone layer.

An annual inspection of the vehicle, including the air conditioning system, may help forestall costly repairs. Many automotive service shops offer AC inspection specials when warm weather arrives. Otherwise, ask your service center to evaluate your system before those hot and humid days of summer.