from Goss’ Garage by Pat Goss

Your car’s air conditioner is busted, it’s ninety degrees, traffic is crawling, you’re sweaty, your clothes are wet and sticky and you, well, you stink; this really sucks. Sitting there sweating your tail off you may not care that the number one cause of poor air conditioner performance is refrigerant loss but it is. Refrigerant is often called Freon®, which is a misnomer because Freon® is actually a DuPont trade name. But no matter what you call it refrigerant leaks and as it leaks cold air becomes cool air and finally, cool air becomes hot air! Note: No matter how many bizarre theories you hear there’s only one possible way for refrigerant to leave your AC system; it has a leak!

Although a loss of refrigerant is responsible for the majority of AC performance issues and is the first thing to check there are lots of other possibilities. That means finding the actual problem requires a systematic diagnosis using an AC refrigerant identifier, pressure gauges and a written diagnostic procedure. Note: Because it’s rarely done, insist that your technician use a temperature and humidity compensation chart to adjust gauge readings or the diagnosis could be totally, expensively wrong. Another mistake is not using a refrigerant identifier which could save hours of diagnostic time. In less than five minutes the identifier identifies improper or contaminated refrigerant, air in the system, and other common conditions that reduce AC performance. A refrigerant identifier should be used on every AC job.

If the temperature and humidity compensated readings are correct and the system has the proper refrigerant have the function of the heater control valve or air-blend door checked as these parts control the temperature of the air coming from the heater and AC. Heater control valves control the flow of hot coolant to the heater and air-blend doors mix hot and cold air together to achieve the desired interior temperature. So although the AC is cooling properly a faulty heater valve or wacky air blend door reheats the cooled air and you get warm air inside the car.

Unfortunately, air-blend door problems are common and often caused by pens, pencils, toys, and other “stuff” you place on the dash. That “stuff” falls through the defroster openings right into the heating and air conditioning ducts. The fix for your mistake is expensive, usually gobbling-up several hours and several hundred dollars.

Air conditioning operates by picking up heat from inside the car and dumping it into air moving through a radiator-like unit mounted behind the car’s grille called a condenser. Because of its position and importance to AC performance have the condenser examined for airflow-restricting dirt and debris yearly and whenever there’s an AC problem. Over time leaves, bugs, mud, and everything from plastic bags to dried road oil and general crud builds up on the condenser itself and between the condenser and radiator. Cleaning the condenser is often all that’s needed to restore proper cooling.

Finally don’t forget to check your cabin air filter. A dirty cabin filter restricts air flow into the cabin and significantly reduces cooling.Note: Never try to top off your system with a kit from the auto parts store. Without test equipment you have no way to know how much refrigerant to add and too much refrigerant can do serious damage. Note: Absolutely never add stop leak.

These are just a few frequently overlooked AC problems that’ll bite ya. To legally fix car air conditioners technicians must have an EPA license and should be ASE certified so ask first. Be wary of “cheap jobs” which often create a mess that is outrageously expensive to fix.