There is never a good time for your air conditioning in your car to stop working, but it typically seems to happen in the dead heat of summer. If your AC system has either quit working or has stopped working well, you're faced with driving your vehicle around with the windows down - which brings little relief when it is hot outside. Having some knowledge about how the air conditioning works in your vehicle can help you get the system functioning again. Show
Part 1 of 9: Understanding the AC system and componentsYour car's air conditioning system works just like a refrigerator or your home air conditioning. The purpose of the system is to remove hot air from the inside of your vehicle. It consists of the following components: Component 1: Compressor. The purpose of the compressor is to pressurize the air conditioning system and circulate the refrigerant. It's located at the front of the engine and is typically driven by the main drive belt. Component 2: Condenser. The condenser is located in the front of the radiator and is used to remove heat from the refrigerant. Component 3: Evaporator. The evaporator is located inside the dash of the vehicle and is used to absorb heat from the interior of the car. Component 4: Metering device. This is known as a metering tube or an expansion valve and can be located either under the dash or under the hood near 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. These consist of metal and rubber lines to carry the refrigerant. Component 6: Refrigerant. Typically, all systems today contain R-134A refrigerant. This can be purchased over the counter at most auto parts stores. Older vehicles were built with R-12, which is no longer used because it contained high amounts of ozone depleting compounds. If you have a license and certification you can still purchase this, though most people opt to retrofit this system to the newer R-134A refrigerant. Though these are the primary components of the air conditioning system, your vehicle has a series of electrical circuits that allow it to function, as well as a dash system that contains numerous doors that move within the dash that can affect effectiveness. Below are the most common causes of poor air conditioning performance and what can be done to get you comfortably back on the road. When performing any air conditioning system service you must have the proper tools - and exercise caution when using them. Reason 1: High 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 well over 150 degrees Fahrenheit so be very careful when coming in contact with parts of the system. Reason 3: Moving parts. You must watch out for moving parts under the hood while the engine is running. Keep all articles of clothing tightly secured. Materials Needed
Part 3 of 9: Performance checkStep 1: Park your vehicle on a level surface. Step 2: Place the wheel chocks around the driver side rear tire. Step 3: Open the hood. Step 4: Locate the air conditioning compressor.
Step 5: Turn on the AC. Turn the air conditioning on in the vehicle and see if that clutch that was previously stationary is now engaged. Step 6: Turn the fan to Medium. If the compressor clutch engaged, return to the inside of your vehicle and turn the fan speed to Medium. Step 7: Check the air temperature. See if the temperature of the air coming from the main dash vents is cold. Read the parts below to understand the different conditions that you may see:
Part 4 of 9: No air comes out of the dash ventsWhen performing your initial check, if air does not come from the center dash vents or if the air is coming from the wrong vents (such as the floor or windshield vents) then you have a problem with the interior climate control system.
Part 5 of 9: The compressor clutch does not engageThe clutch may not engage for several reasons, the most common being low refrigerant in the system, but it may also be an electrical issue. Reason 1: Voltage. Voltage is not sent to the clutch when the air conditioning is turned on due to an open circuit in the electrical circuit. Reason 2: Pressure switch. An air conditioning system pressure switch can disrupt the circuit if certain pressures are not met or if the switch is failing. Reason 3: Input issue. More up to date systems are computer controlled and use numerous other inputs including vehicle interior and exterior temperature to determine whether or not to turn the compressor on. You need to determine if there is refrigerant in the system. Step 1: Turn the engine off. Step 2: Install the gauges. Install the gauge set by locating the high and low side quick connections.
Step 3: Observe the pressure readings on the gauges.
Part 6 of 9: The clutch engages but the air is not coldStep 1: Turn the engine off and install the gauge set. Step 2: Restart the engine and turn on the air conditioning. Step 3: Observe the pressure readings.
Part 7 of 9: The system is emptyMaterials Needed
If there was not pressure found during your test then the system is empty and there is a leak.
Part 8 of 9: The system is low
Step 1: Turn off the engine. Step 2: Disconnect low side gauge. Disconnect the gauge set from the low side port.
Step 3: Install charge kit. Install the charging kit to the low side connection on the AC system. Step 4: Turn on engine. Turn on the engine and the air conditioning. Step 5: Observe. Observe the gauge on the kit and begin adding the refrigerant whether it be with a button or a trigger on the kit.
Step 6: Reach desired pressure. Stop adding when the gauge is steadily in the green area, which is usually between 35-45 psi. Allow the system to continue running and check the temperature of the air coming out of the dash vents making sure it is cold. Step 7: Disconnect the charging hose. You have now filled the system with refrigerant. Make sure that you do not overcharge the system as too much refrigerant is just as bad - if not worse - than too little. Part 9 of 9: The air conditioning still does not work
This system can be extremely complex, and takes numerous other tools and repair manuals to correctly diagnose in most vehicles. If performing these steps did not achieve cold air from your vents or you are not comfortable with doing this work, you need to enlist the help of a certified mechanic who has the tools and the knowledge to test your air conditioning system. The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details How do I check the Freon level in my car AC?Place the thermometer in the center vent of your vehicle and allow the car to run for a few minutes. Read the gauges once the pressures stabilize. The low port should read between 25psi and 45psi, and the high port should read between 250psi and 400psi. If both are low, you are likely low on refrigerant.
How do I know if my car AC is low or high pressure?To gauge the pressure, hook up a gauge set to the AC system and record the pressures of both low and high sides. Check the ambient temperature and see if the pressures match the numbers on the pressure chart. Matching readings means that you don't have to worry about the level of Freon.
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