How to Diagnose Your Vehicle's Air Conditioning System

There is never a good moment when the air conditioner in the car stops working, but usually it happens in the height of summer. If your air conditioning system has stopped working or has stopped working normally, you are experiencing…

There is never a good moment when the air conditioner in the car stops working, but usually it happens in the height of summer. If your air conditioning system has either stopped working or has stopped working normally, you've found yourself driving your car with the windows down, which isn't much relief when it's hot outside. With some knowledge of how your car's air conditioner works, you can help you get your system back up and running.

Part 1 of 9: General information about the air conditioning system and its components

Your car's air conditioning system works just like a refrigerator or home air conditioner. The purpose of the system is to remove hot air from the interior of your vehicle. It consists of the following components:

Component 1: Compressor. The compressor is designed to increase the pressure in the air conditioning system and circulate the refrigerant. It is located at the front of the engine and is usually driven by the main drive belt.

Component 2: Capacitor. The condenser is located in front of the radiator and serves to remove heat from the refrigerant.

Component 3: Evaporator. The evaporator is located inside the car's dashboard and is used to absorb heat from the car's interior.

Component 4: Measuring device. It is known as a gauge tube or expansion valve and can be located either under the dashboard or under the hood next to the fire wall. Its purpose is to change the pressure in the air conditioning system from high pressure to low pressure.

Component 5: Hoses or lines. They consist of metal and rubber piping for the refrigerant supply.

Component 6: Refrigerant. As a rule, all modern systems contain R-134A refrigerant. It can be purchased without a prescription at most auto parts stores. Older cars were built with R-12 refrigerant, which is no longer used because it contains a large amount of compounds that deplete the ozone layer. If you are licensed and certified, you can still purchase one, although most people choose to upgrade this system to the newer R-134A refrigerant.

While these are the main components of an air conditioning system, there are a number of electrical circuits in your car that allow it to function, as well as a dashboard system that contains many doors that move inside the dashboard, which can affect efficiency. Below are the most common causes of poor air conditioning performance and steps you can take to get back on the road comfortably.

When performing any maintenance on the air conditioning system, you must have the proper tools and be careful when using them.

Reason 1: High blood pressure. The air conditioning system is filled with high pressure refrigerant and can operate at over 200 psi, which can be very dangerous.

Reason 2: High temperature. Parts of the AC system can reach over 150 degrees Fahrenheit, so be very careful when coming into contact with parts of the system.

Reason 3: moving parts. You must watch the moving parts under the hood while the engine is running. All items of clothing must be securely fastened.

Necessary materials

• A/C Manifold Gauge Set
• Gloves
• refrigeration
• Protective glasses

• Wheel pads

• A warning: Never add anything other than the recommended refrigerant to the A/C system.

• A warning: Always wear safety goggles when servicing any pressurized system.

• A warning: Never install pressure gauges while the system is running.

Part 3 of 9: Performance Check

Step 1: Park your car on a level surface..

Step 2: Install wheel chocks around the rear wheel on the driver's side..

Step 3: open the hood.

Step 4: Find the A/C Compressor.

• Functions: The compressor will be mounted towards the front of the engine and driven by the engine drive belt. You may need a flashlight to see it. This is one of the largest pulleys in the system and has a separate clutch located at the front of the compressor. Two lines will also be connected to it. If you have trouble finding it, start the engine and turn off the air conditioner. The compressor pulley will rotate with the belt, but you should notice that the front of the compressor clutch is stationary.
  
  

Step 5: Turn on the AC. Turn on the air conditioner in the car and see if the clutch that used to be stationary is engaged.

Step 6. Turn on the fan to a medium level.. If the compressor clutch has engaged, return to the inside of the vehicle and set the fan speed to medium.

Step 7: Check the air temperature. Check if the temperature of the air coming from the main vents is low.

Read the parts below to understand the different conditions you may see:

• No air coming out of vents
• Compressor clutch not working
• Clutch engages but air is not cold
• System empty on refrigerant
• Low refrigerant in system

Part 4 of 9: Air won't come out of dashboard vents

When performing the initial check, if air is not coming from the center vents on the dashboard, or if air is coming from the wrong vents (such as floor vents or windshield vents), you have a problem with the interior climate control system.

• Airflow problems can be caused by anything from a fan motor problem to electrical problems or module failure. This needs to be diagnosed separately.

Part 5 of 9: Compressor Clutch Won't Engage

The clutch may fail for several reasons, the most common being low coolant levels in the system, but it could also be an electrical problem.

Reason 1: Tension. Voltage is not supplied to the clutch when the air conditioner is turned on due to an open circuit in the electrical circuit.

Reason 2: Pressure switch. The air conditioning pressure switch may break the circuit if certain pressures are not met or if the switch is faulty.

Reason 3: input problem. More modern systems are computer controlled and use a variety of other inputs, including the car's interior and exterior temperatures, to determine whether the compressor should be turned on.

Determine if there is refrigerant in the system.

Step 1: Turn off the engine.

Step 2: Install the sensors. Install the gauge set by locating the high and low side quick connectors.

• Functions: Their location varies on different vehicles, but in most cases you will find the lower side on the passenger side in the engine bay and the higher side in front. Fittings are sized differently so you will not be able to install a sensor installed backwards.
  
  

Step 3: Watch the Pressure Gauges.

• A warning: Do not check the pressure by pressing on the fitting to see if refrigerant comes out. This is dangerous and releasing refrigerant into the atmosphere is illegal.

• If the reading is zero, you have a large leak.

• If there is pressure but the reading is below 50 psi, the system is low and may just need to be recharged.

• If the reading is above 50 psi and the compressor does not turn on, then the problem is either in the compressor or in the electrical system that needs to be diagnosed.

Part 6 of 9: Clutch engages but air is not cold

Step 1: Turn off the engine and install the sensor kit.

Step 2: Restart the engine and turn on the air conditioner..

Step 3: Watch Your Pressure Readings.

• Although each air conditioning system is different, you want to have pressure on the high pressure side of about 20 psi and on the low side of about 40 psi.

• If both the high and low sides are below this reading, you may need to add refrigerant.

• If the reading is very high, you may have an air entry problem or a condenser airflow problem.

• If the pressure does not change at all when the compressor is turned on, then the compressor has failed or there is a problem with the metering device.

Part 7 of 9: The system is empty

Necessary materials

• Cooling Dye

If no pressure is detected during the test, the system is empty and there is a leak.

• Most air conditioning system leaks are small and hard to find.

• The most effective way to contain a leak is to use a refrigerant dye. Dye kits are available at most auto parts stores.

• Using the manufacturer's instructions, inject the dye into the air conditioning system. This is usually done through a low pressure service port.

• Let the dye penetrate the system.

• Using the included UV light and goggles, you will inspect all components and hoses of the air conditioning system and look for luminous materials.

• Most dyes are either orange or yellow.

• Once you find a leak, fix it as needed.

• If the system was empty, it must be completely emptied and recharged.

Part 8 of 9: System Low

• When adding refrigerant to a system, you want to do it slowly because you don't know how much you actually need.

• When the shop performs this duty, they use a machine that draws the refrigerant out of the system, weighs it, and then lets the technician add the exact amount of refrigerant back into the system.

• Most store-bought refrigerant kits come with their own charging hose and pressure gauge, allowing you to add refrigerant yourself.

Step 1: Turn off the engine.

Step 2: Disconnect the lower gauge. Disconnect the gauge set from the port on the low pressure side.

• FunctionsA: You should only charge on the low side to prevent injury.

Step 3: Install the charging kit. Install the charging kit on the connection on the low voltage side of the AC system.

Step 4: Turn on the engine. Turn on the engine and air conditioner.

Step 5: Observe. Watch the gauge on the kit and start adding refrigerant, whether it's a button or a trigger on the kit.

• Functions: Add refrigerant in small increments, checking the charge scale between applications.

Step 6: Reach Your Desired Pressure. Stop adding when the gauge is steadily in the green zone, which is usually between 35-45 psi. Let the system continue and check the temperature of the air leaving the instrument panel vents, making sure it is cold.

Step 7: Disconnect the charging hose.

You have filled the system with refrigerant. Make sure you don't overcharge the system, as too much refrigerant is just as bad, if not worse, than too little.

Part 9 of 9: Air conditioning still not working

• If the air conditioner still does not work properly, further testing is needed.

• A warningA: You must have a special license to legally service the air conditioning system.

This system can be extremely complex and many other tools and repair manuals are required to properly diagnose most vehicles. If following these steps did not result in cold air coming out of the vents, or if you are not comfortable doing the job, you will need to enlist the help of a certified mechanic who has the tools and knowledge to inspect your air conditioning system.