Common Car AC Problems and How to Fix Them

Learn the five most common car AC problems and the symptoms they cause

Car air conditioning (A/C) systems are vital for comfort, especially during hot weather. But they can encounter these five common car AC problems as the vehicles age. The single most common cause of car AC problems is a low refrigerant level due to refrigerant leaks. DIYers often refill their car’s AC without addressing the leak, but that can lead to even more costly failures down the road.  This article covers each of the five common failures.

Refrigerant Leaks are the #1 cause of car AC problems

When refrigerant leaks out of the system, cooling efficiency drops significantly. Over time, hoses and seals can deteriorate, leading to gradual refrigerant loss. Once that happens, a car’s AC system can leak refrigerant from rubber seals, hoses, joint connections, or even the condenser itself. Detecting and repairing these leaks promptly is crucial to maintaining a properly functioning air conditioning system.

The refrigerant carries the oil throughout the system to lubricate the compressor seals. When refrigerant leaks out, so does some oil.  Once you lose oil, you start to wear the compressor. If you add more refrigerant from an AC recharge kit, you’ll get colder air, but unless you replace the oil you lost, your system is headed for an early grave.

Learn the symptoms of a low refrigerant charge

• The air never gets real cold— You notice the air is cooler than outside air, but it’s not cold like when the system is operating properly.
• It takes a long time for the air to get cold— A low refrigerant charge can’t cool effectively, so it takes a long time to reduce cabin temperature
• The air is only cold when the car is moving— This can be caused by a low refrigerant charge or a faulty radiator fan. If the AC has a low charge, the lowered efficiency and compressor speed at idle can’t keep the evaporator cold enough to produce enough cold air.
• You have cold air, and then no air comes out of your vents— A low refrigerant charge can cause evaporator icing. When that happens, the ice blocks most or all of the airflow.

Compressor Issues are the 2nd leading cause of car AC problems

The compressor is often called the heart of the air conditioning system. It pressurizes the refrigerant and circulates it through the system. Compressor failure can stem from various issues, the most important being a lack of lubrication due to a refrigerant leak. But an AC compressor can also fail due to a clutch issue, pulley bearing, front shaft seal leak, case leak, bad flow valve, or just plain wear and tear.

As a compressor wears due to lack of lubrication, the metallic wear particles spread through the system. Any air in the system causes the particles to oxidize and turn black, which is why this type of compressor failure is referred to as black death.

ac compressor black death

Learn the symptoms of compressor failure

• No cold air— This is typically caused by a failed clutch or a faulty pressure regulator valve.

• Cool but not cold air— A worn compressor can’t compress efficiently, so the air doesn’t get as cold.

• Unusual noises— A failing compressor can cause squealing or crunching/grinding noises, indicating a mechanical failure.

Moisture in the system is the 3rd most common cause of car AC problems

Any time air enters the system, it carries moisture into the system as well. Moisture reacts with the refrigerant and oil to form an acidic emulsion that not only coats the inside of the condenser and evaporator but also starves the compressor for lubrication.

Moisture can cause the expansion valve to freeze shut, preventing cooling, and the emulsion sludge it creates can clog the screen on orifice tube systems.

New and clogged AC orifice tube. Clogged tube shows evidence of “Black Death.”

A Clogged or Dirty Condenser or Non-functioning radiator fans are the 4th leading cause of car AC problems

The condenser removes heat from the refrigerant, causing it to cool and condense back into a liquid. Over time, dirt, debris, and contaminants can accumulate on the condenser’s fins, hindering its heat exchange efficiency. A clogged or dirty condenser can result in reduced cooling performance and cause the system to struggle to maintain the desired temperature. Also, if the radiator fans aren’t operating properly, pressure in the condenser will rise to the point where the high-pressure switch shuts off the compressor.

Electrical Malfunctions cause car AC problems

Modern auto air conditioning systems are complex and reliant on electronic components. Electrical malfunctions, such as blown fuses, faulty sensors, relays, or wiring problems, can disrupt the system’s functioning. For instance, a malfunctioning temperature sensor might inaccurately gauge the cabin temperature, causing the system to behave erratically.

Click here to learn how to diagnose and fix your car’s AC yourself

©, 2023 Rick Muscoplat