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Troubleshooting the most common AC issues in your car

Troubleshooting the most common AC issues in your car

Anyone who has traveled in a car during the sizzling days of summer when the air conditioner is broken knows how miserable the experience can be. One who has suffered through such an occasion also knows how imperative it is to keep the AC in good working order so that such things don’t occur. 

Many if not most people who own a car may outsource the troubleshooting and repair of these problems to a neighborhood mechanic. However, if you are skilled in performing work on your car and have the knowledge it takes to figure out what’s wrong and how to fix it, you may want to do the troubleshooting and repair yourself.

 Common Problems Concerning Your Car’s AC

 Knowledge comes in when you need to diagnose a problem. In these situations you need some idea of how a car AC works and what problems commonly occur.

 The skill comes in when you do the repair.

 Some of the most common issues concerning your car’s AC include:

  • Moisture.  Of course, the purpose of a car air conditioner is to lower the ambient temperature. To achieve this the AC is forcing warm air outside the car and is drying and cleaning the air as well as cooling it inside the car. At times moisture or debris can contaminate the AC causing it to fail.
  • Foul smell. This occurs when bacteria, fungi, and microorganisms develop within the AC when it is not in use. This happens because its interior is dark and damp, which is an ideal condition for these critters to appear and flourish and that results in an unpleasant odor.
  • Low refrigeration. It is the refrigerate (or Freon) in the air conditioner that cools the interior of the car. The level of refrigerate can diminish as much as 15% a year. Surprisingly, this occurs more during the winter when the AC is not being used because its seals dry out, which affects the unit’s productivity causing it to dissipate more refrigerate quickly.
  • Dirty Condenser. Dirt, grime, or debris can restrict the airflow of the AC resulting in no cooling.
  • Mechanical Issue. An air conditioner part including the compressor clutch, pressure switch or a valve that isn’t working can result in poor cooling or no cooling at all.
  • If the pressure in the AC is low, there may be a leak.

 If refrigerate must be evacuated and recycled, it is suggested that you assign the task of fixing your car’s AC to a professional mechanic.

 Tools You Will Need To Troubleshoot And Repair A Car’s AC

You need to take caution when working on a car’s AC system because it is under high pressure. So it is important for you to wear protective clothing when undertaking the task. Such clothing includes:

  •  Gloves
  • Goggles
  • Face shield
  • Apron

 Tools or other equipment you need include:

  •  The car’s air conditioner’s service manual
  • Refrigerant
  • Thermometer
  • Pressure gauges
  • Charge hose
  • Leak detector or dye
  • Clean rag

Refrigerant can be found at an automotive parts store. Make sure that you acquire the proper refrigerant for your car. Vehicles manufactured after 1995 use R134a refrigerant. If your vehicle was manufactured prior to 1995, then it probably needs R12 refrigerant.

As far as the pressure gauges are concerned, there are two different types –- a single gauge that connects to the low-pressure port only and allows recharging of the system or high and low pressure gauges. The single gauge is the least expensive alternative, but the high and low pressure gauges are suggested.

The charge hose is designed to screw onto the can of refrigerant and into the gauge block. The hose includes a valve that punches a hole into the top of the refrigerant can so that its contents can flow into the AC system.

Diagnosing And Repairing Air Conditioner Problems

The first thing you need to do is identify the problem.  The steps to do this include:


  1. Start the vehicle and turn on the AC.
  2. Feel the air coming out of a duct to determine whether it is warm, cool, or cold. If the air is warm to cool, but not cold, the problem could be the airflow. You may have to replace the cabin air filter to increase airflow.
  3. Observe the cooling fans on the radiator to see if they are running. If they are not, there may be an electrical issue.
  4. Locate the air conditioner in the engine compartment and observe if the center of the pulley and the pulley itself are turning. When the clutch is engaged the center of the pulley and the pulley will rotate. If the clutch does not engage, the AC compressor may be damaged and needs to be replaced or it may need to be filled with refrigerant.
  5. Most compressors have a wire leading to the electric clutch. Find the connector in the middle of that wire and unplug it. Take a length of wire and run it from the compressor to the positive terminal of the battery. If you hear a loud CLACK, the electric clutch is working properly. If not, the clutch will need to be replaced. Since replacing the compressor needs specialized tools it is recommended that you take your vehicle to a professional mechanic to replace the compressor or clutch.
  6. Use the leak detector kit to determine if there is a leak in the AC. The kit includes a dye that can run through the lines and seek out any leaks or cracks so that you can observe them. If you find leaks, then it is suggested that you take the vehicle to a mechanic who can repair the problem. If there are no leaks, then the issue may be low refrigerant.
  7. If your car requires R12 refrigerant, then it is suggested that you take the car to an auto repair specialist to convert it to R134a.
  8. Use the thermometer to read the temperature of the interior of the car. Once done, use the gauge to read the temperature of the refrigerant. Refrigerant occupies different amount of space within the can and air conditioning system at different temperatures, causing the gauge to read differently at different times. If you know the ambient temperature, then you will know the proper reading of the gauge on the refrigerant can. When refrigerant expands and takes up more space it increases the pressure in the can.
  9. The AC has two service ports –- a low side port and a high side port. To recharge the AC, locate the low side service port. Follow the lines from the AC compressor to a nozzle near the bottom of the car. This is the low side service port.
  10. Use a rag to clean the area around the service port. Be careful not to clog the port with grime or debris while cleaning. Wipe the cap and the line first, then remove the cap and wipe off the port.
  11. Connect the charging hose to the low side service port. Connect the opposite end of the hose to the can. The hose should be connected to the nozzle on the gauge and then to the can.
  12. Read the instructions on the refrigerant can to determine how to read the gauge.
  13. While taking the ambient temperature read the air pressure chart on the gauge to determine pressure. Once you begin spraying the refrigerant into the nozzle continue to observe the gauge to determine when the system is full.

 Refilling The Refrigerant

 Here are step-by-step instructions on refilling a car AC with refrigerant. 

  1. Turn the valve on the top of the refrigerant can clockwise until the top of the can is punctured.
  2. Start releasing the refrigerant through the hose and into the AC.
  3. Hold the can upright and shake periodically as the refrigerant passes through into the vehicle’s engine. Make sure you don’t turn the can to the side because the pressure within the can will drop resulting in failure to refill the AC system.
  4. As you refill look for leaks in the system. If you spot a leak, a professional mechanic will need to repair it. Note where the leak is located to make it easier to find and repair.
  5. Once the gauge reads full, remove the hose from the port and return the cap. If there is refrigerant left, keep it in a cool place so that you can use it to recharge another vehicle or to recharge the same vehicle later. Make sure that the can is not leaking prior to storage. If the can is empty, throw it away.
  6. If you observed a leak or the AC compressor does not engage, take the vehicle to a professional mechanic so that the compressor can be repaired.

Finally, be careful when repairing refrigerant leaks because the temperature of the substance is so cold it could injure you.

If you discover that the AC condenser is dirty, use a flushing agent that vaporizes quickly and does not leave a residue in the system to clean it. If the condenser is old or has been causing you problems, replace it.

It is also a good idea to periodically check the compressor, compressor clutch switch, fuses, wires, fan belt, and compressor seal to be sure they are working properly. You should also inspect the oil in the compressor to determine if it is contaminated. Flush out the unit to evacuate old oil before putting in new oil.

Many components of the AC are susceptible to wear and tear and could fail as a result. To prevent problems regularly replace such parts as the expansion valve, accumulators and receiver driers if you notice they are deteriorating. 

Here at Pro Tool Shopper, we carry all the necessary AC tools for leak detection, recharging, etc, and all of the major brands like S.U.R.&R. and Bright Solutions.  Check out our catalog today and call if you need something and don't see it.