A: Air conditioning systems use the environmentally friendly R-134a refrigerant, which is not compatible with R-12 system components. When replacing components, add refrigerant oil equal to the amount removed from the component being replaced. Regular maintenance checks include inspecting the drivebelt, checking its tension, inspecting system hoses for damage or wear, cleaning the condenser fins, ensuring the correct refrigerant charge, and checking the evaporator housing drain tube. It's beneficial to operate the system for ten minutes monthly, especially during winter. Troubleshooting in-depth issues requires specialized equipment. Poor cooling often results from a low refrigerant charge. To check, warm the engine, set the air conditioning to the coldest and highest blower setting, and feel the evaporator's larger pipe. The pipe should be cold. Also, using a thermometer, the output air should be 35 to 40 degrees F below the ambient air temperature. Adding refrigerant requires an R-134a charging kit. Never add more than one can of refrigerant. During the charging process, the compressor should be running, and the refrigerant can should be shaken occasionally. Properly charged systems should cool to approximately 40 degrees F. If the carpet under the Heater Core is damp, or if there's antifreeze vapor, the heater core is leaking. A non-warming heater might be due to a stuck thermostat, blockage in the system, or a heater core issue. Unpleasant air conditioning odors are usually due to fungus growth on the evaporator core. Effective treatments require specific aerosol disinfectants. The disinfectant is sprayed into an intake port inside the cabin filter housing, covering the evaporator core's entire surface. Keeping the evaporator housing drain tube clear prevents mildew. Some vehicles have an automatic climate control system, which is complex and best handled by professionals.