Mar. 17, 2025
You're thankful your car A/C helps keep the cabin cool on sweltering summer days. But do you understand how the A/C system works and how to keep it maintained? This guide covers the nitty gritty details of your vehicle's A/C to help you catch problems early on and keep it in excellent shape.
You will get efficient and thoughtful service from Sino Air Conditioner.
Believe it or not, there's no ice machine hidden inside your car A/C. That blast of chilly air is actually hot air with the heat removed during a multi-step process.
When you turn the A/C on, the compressor compresses the system's refrigerant, raising its pressure and temperature. The refrigerant loses heat as it flows through the condenser. Typically, it then passes through the receiver/dryer, where contaminants and moisture are removed.
Then, it's on to the expansion valve. Here, the refrigerant loses pressure and temperature as it enters the evaporator, chilling it.
The evaporator is like a mini radiator in the dashboard. Air gets blown through the chilled evaporator, which cools and removes moisture from the air. The ventilation system blows that cool, dry air into the passenger compartment. Your air conditioning system works hard so you can get that refreshing, cold air.
There's no set schedule for inspecting your A/C ' it's all about how the system feels. Are you refreshed and cooled with full airflow when your vehicle's A/C is pumping? If you answered, 'Yes, I am as cool as a cucumber,' you can cross A/C inspection off your list.
Do you fall into the 'my A/C is not cold enough' or the 'my A/C doesn't work in the heat' side of the spectrum? Don't sweat; stop in for an A/C Performance Check, and we'll have you back on those hot summer streets cooler than ever.
Modern air conditioning systems don't need to be recharged on a set schedule. Most drivers can go years before needing one. However, you'll likely notice when it's time for a recharge. Signs your A/C might need to be recharged include hot or warm air coming from the vents, refrigerant leak, weird smells coming from the vents, and an A/C clutch that won't engage. (We'll cover all of these potential symptoms below!)
If you experience any of these problems, visit your local Firestone Complete Auto Care for an A/C Performance Check. Our expert technicians will get to the root of the problem.
To help keep your cabin cool, your A/C relies on several components. Let's take a closer look at these A/C system parts and their roles in giving you that refreshing blast of cool air.
The compressor is the core, primary part of every A/C system. They control temperature output with an electrically operated clutch. This clutch turns on and off whenever you change the temperature or if the HVAC module senses it has reached the desired temperature. If the ambient air temperature drops below the programmed value, the compressor clutch may not engage.
Before the compressor turns on, a special electromagnetic clutch (the compressor clutch) engages and disengages the compressor cycle. The compressor clutch engages the compressor, turning it on or off when commanded.
Consider the A/C condenser the master of turning hot refrigerant gasses into liquid. The condenser is mounted at the front of most vehicles, usually in front of the radiator. Outside ambient air passes through the condenser, condensing and cooling the hot refrigerant gas into a cool liquid refrigerant.
The receiver/drier is found on vehicles with a thermal expansion valve. It's the safety net responsible for helping trap and prevent harmful debris and moisture from reaching the compressor and other vital A/C parts. The receiver/drier should be replaced anytime the A/C system is opened for repair or if a technician determines moisture or debris has damaged your receiver/dryer performance.
An accumulator is similar to a receiver/drier but is only on vehicles with an orifice tube. If you have an accumulator, you do not have a thermal expansion valve.
The accumulator:
You will need to replace the accumulator if the A/C system is opened for repair or if a technician determines moisture or debris has damaged your accumulator's performance.
The orifice tube or thermal expansion valve is located between the condenser and the evaporator. It constantly monitors the pressure and temperature of your A/C system to determine the exact amount of refrigerant that can safely enter your evaporator. If too much or too little refrigerant enters the evaporator, you could have a big problem.
An orifice tube may also contain a fine mesh screen to block contaminants from the rest of the system.
The evaporator is located behind your dash and is responsible for cooling cabin air and removing moisture. Low-pressure refrigerant traveling through the evaporator cools it. This allows the evaporator to absorb heat from the cabin air, dropping the temperature of the air blowing out of the vents. If cold, refreshing air hits your face, the evaporator is working like a champ.
The clutch cycling switch cycles the compressor according to the pressure in the accumulator. This action helps to prevent the evaporator from freezing. Although most cars can blow air at temperatures as low as 60 degrees, the temperatures inside the evaporator core can get cold enough to freeze the entire core completely.
The clutch cycle's job is to ensure the evaporator doesn't reach the point of glacier temperatures.
Refrigerant (often referred to by the DuPont trade name Freon) is a specially formulated cooling agent that can transform from a liquid to a gas and back again. It absorbs and releases heat, ultimately leaving cool air behind.
Different devices, such as your home refrigerator, home A/C system, or vehicle, may use different refrigerants. They may or may not be the same.
The three common car refrigerants are R-12, R-134a, and R-yf. Different refrigerant types require different charging hoses, so check which one your vehicle is it in earlier models.
The refrigerant service port is the connection point where new refrigerant can enter the system during an A/C system recharge or where you can remove refrigerant from the A/C system. There is a service port located on the low side and high side A/C lines. Only properly equipped, certified, and qualified persons should perform A/C recharging services. The EPA (Environmental Protection Agency) requires anyone who services automobile air conditioning systems to be EPA Section 609 Certified.
If the compressor is engaging, the center of the compressor clutch will turn with the outer pulley. If the pulley does not turn and there is a loud squeal, this usually indicates a locked up compressor. The compressor and drier will need to be replaced.
If the vehicle's refrigerant is low, the low pressure cut-out or low pressure cycling switch can prevent the clutch from engaging. Adding refrigerant should alleviate the problem.
You can tell if you compressor is cycling on and off by looking at the clutch (or belt pulley) at the front of the compressor. The center of this clutch should be spinning when the compressor cycles on. Please note that the pulley itself will always spin while the center of the clutch may not.
When you overcharge your vehicle's A/C system, a pressure cut-off switch is activated to stop the A/C compressor from running. In turn, this will cause the system to blow warm air. If this happens, you will need to bring your vehicle to a certified A/C professional or technician to have the excess refrigerant recovered (i.e., removed) from the system. Remember that it is illegal to vent refrigerant from your system into the atmosphere, and the government can impose stiff fines for failure to follow this law.
In order to prepare a new compressor for installation, it will need to be primed. Not doing so may cause serious damage and void the compressor's warranty. Priming a compressor involves adding oil to both the receiver-dryer and suction port of the compressor to lubricate it for use. Prior to starting the process, it is vital to know the oil capacity for both the system and the compressor prior to starting. This information can be found on our Spec Database.
Once you have determined the proper amount of lubricant your compressor needs, pour half of the specified into the suction port of the compressor and the other half into the receiver-dryer. After the compressor is installed into the vehicle, you will need to rotate the compressor clutch 10 to 20 times to ensure that the oil is properly distributed throughout the system and the compressor. Tools will be required for this. Be careful to not turn the compressor nut in the middle of the pulley as it may affect the air clearance between the clutch pulley and the clutch faceplate. After you have rotated the pulley 10 to 20 complete revolutions, the priming procedure will be complete and the compressor will be properly primed.
Yes, but only specific products. Be sure to check the label on each individual A/C Pro® item to assure best use practices.
Unfortunately, the caps on the high and low pressure automotive air conditioning service ports vary. In most cases, both caps will be black, but we have also seen them in grey, blue, and green. Sometimes they have an 'H' or 'L' to indicate High or Low pressure ports.
To find where the low-side service port is located on your vehicle's air conditioning system, look for the valve that is located on the line that runs from the compressor through the evaporator and up to the condenser on the low-pressure (suction) side of the system. These ports are sometimes covered with a cap marked 'L' for 'Low.' Note that R-134a recharge hoses have couplers that will only fit on the low-side service port of R-134a systems, and the same goes for both R-12 and R-yf. If you don't know where your low-side service port is you can locate it using our Port Locator tool.
The EPA requires that ANY replacement refrigerant MUST have unique fittings, charging devices and label. Therefore, the EPA states that 'drop in' refrigerants are illegal. Furthermore, only R-134a has been tested and approved by the original equipment manufacturers.
No. Federal law prohibits topping off an R-12 system with something other than R-12 refrigerant. Your options are to locate some R-12 refrigerant if you are certified to purchase, then add it with an R-12 recharge hose. Or you can convert the system using one of our R-134a retrofit kits that will allow you to now add 134a refrigerant to your automotive air conditioning system. You will have to make sure that you remove any residual R-12 refrigerant by having it evacuated prior to retrofitting your vehicle.
The answer here is two-fold. It's possible that the system has a small leak and is now low on refrigerant, which will allow the system to blow cold but now as cold as it used to. In this case, start by checking the system pressure via the low-side port. If it's low, add refrigerant or a refrigerant with a stop leak to correct the system pressure. If the pressure is correct, adding additional refrigerant will not make the system blow out colder and will in fact cause the system to be overcharged. This will result in the system working less efficiently and warmer air will blow from the vents.
All A/C Pro® products contain the proper ratio of replacement oil.
A pressure gauge must be used to determine the accurate system pressure and thus amount of fill. All A/C Pro® gauges indicate whether you should continue filling (charging) or not.
If you are replacing a component part in the system or if the pressure gauge indicates that the A/C system pressure is lower than 10 PSI, it should be vacuumed prior to charging. If you do not know how to vacuum your A/C system, consult a professional certified technician.
When checking low-side pressure you will get two different pressure readings, one when the compressor cycles on and one when the compressor cycles off. Use the pressure reading when the compressor is cycled on and the system is operating at its highest settings (temperature to maximum cold and fan on high). When the compressor cycles on you should see the needle on your pressure gauge begin to drop. When the compressor turns off you will see the needle move back to a higher pressure. Take the reading that occurs when the pressure is at its lowest point when the compressor is cycled on.
Ambient temperature is simply the temperature of the air surrounding the car. Be sure to check out our Refrigerant Pressure Charts for more information.
Follow these steps, and always remember to wear safety glasses and gloves when recharging your vehicle's A/C:
No. The refrigerant in your vehicle's air conditioning system never goes bad and never gets 'used up,' so if your vehicle's A/C system pressure is low it means there is a leak. This will need to be repaired in order for your vehicle's system to hold refrigerant. If the system is able to maintain a charge for a period of two weeks or longer, it is possible to seal the leak with sealant such as A/C Pro® Super Seal. If it will not hold a charge for at least two weeks, it is recommended that a professional technician is sought out to help find and repair the leak.
Not only is overcharging your system potentially dangerous, but an overcharged system will also not function properly and can seriously damage your A/C compressor or other component parts. The symptoms of an overcharged A/C system are the same as a system that is undercharged: Warm air out of the vents.
To prevent overcharging your A/C system it is imperative to measure the pressure before beginning to charge it. To measure the pressure in the A/C system, attach a pressure gauge to the low side port. Your car must be running with the A/C system set to maximum cool and the fan in its highest setting. It is important to note that the proper pressure in your A/C system is dependent on the ambient (outside) temperature. To determine the proper pressure for your system, consult a pressure chart such as this one, or set the bezel arrow on your pressure gauge to the corresponding ambient temperature and charge to the pressure corresponding to that temperature setting. If the outside temperature is at or below 55°F do not charge your car. Also, never charge your vehicle above 55 PSI.
Unfortunately, the caps on the high- and low-pressure automotive air conditioning service ports vary. In most cases, both caps will be black, but we have also seen them in gray, blue, and green. Sometimes they have an 'H' or 'L' to indicate high- or low-pressure ports.
Wondering where your car or truck's low-pressure port is located? Use our Port Locator.
No. Your car's A/C refrigerant never goes bad. Nor do you 'use up' the refrigerant that is in your system. If your vehicle's A/C system pressure is low, your vehicle has a refrigerant leak and that leak will need to be repaired in order for your system to hold refrigerant. If your vehicle is able to maintain a charge for a period of two weeks or longer, then it is possible to seal the leak with sealant such as Super Seal. If your system will not hold a charge for at least a two week period then it is advisable to seek professional assistance to find and repair the leak.
Vent temperature will vary. Some newer cars may have vent temperatures that are below 50°F while older model cars' vent temperatures may be in the mid-50's to low 60's.
Yes! This is one of the easiest jobs that you can do yourself on your vehicle. Please click through the following FAQs to learn how you recharge your AC using our products:
Please feel free to call our technical support line for further help at 888-318-.
If the vehicle has a fully electric compressor (no belt-driven pulley) then you can use some of our products which have been developed specifically for hybrid and electric vehicles. As a rule of thumb, on hybrid vehicles you should ONLY use hybrid lubricant and straight refrigerant, however A/C Pro® has your back. Refer to our individual product pages for more information and to find what specific products can be used on your vehicle.
To properly charge you automotive A/C system the ambient temperature should be above 65ºF. Anything below that does not allow the system to build up enough pressure for a proper reading on your A/C Pro® pressure gauge. Because of this, adding refrigerant to your vehicle is not recommended when the ambient temperature is under 65ºF.
No. While our new universal gauges work with both types of valve systems, they do not make a piercing valve act like a self-sealing valve. If you are using a piercing can, you will want to keep your gauge attached to the can until it is depleted.
There are several possibilities behind why this is happening. One is that the compressor may be damaged and thus not working properly. You can check to see if it is cycling on and off properly by looking at the clutch faceplate in the middle of the compressor pulley. If your compressor is not cycling on, you should seek the help of a certified A/C professional immediately. Ignoring the problem will not make it go away and in fact can worsen the situation.
Contact us to discuss your requirements of Vehicle Air Conditoning System Parts. Our experienced sales team can help you identify the options that best suit your needs.
Other possible causes are blown relays and fuses, defective sensors, and stuck blend doors. Seek the help of a certified A/C professional to assist in determining the cause.
No. Not only is it harmful to the environment to vent refrigerant into the atmosphere, it is also illegal. Violation of this Federal Law may carry a fine of up to $25,000. If you need to recover refrigerant from your system please seek the help of a qualified service technician.
The smiley face on the bottom of the can is a pressure relief vent to help release the pressure of the can should it become overheated. The refrigerant in the can is a high-pressure gas and, as with any gas, it expands when heated. You should never leave or store any cans of refrigerant in your vehicle as they can overhead and rupture the can. Always store cans of refrigerant in a cool, dry location.
The blue bezel turns on the gauge so that you can set the pressure range as it relates to the outside temperature. Here is how it works: determine the outside temperature around your car. Turn the bezel so that the arrow points to the outside temperature. Notice the 'V' shape on the dial.
This is the appropriate pressure range based on the ambient (outside) temperature. When reading the pressure, if the arrow is below the range then charge the car until the needle on the pressure gauge is in the range. If it is above the upper end of the range your system is overcharged. In this case you should seek the help of a qualified technician to recover refrigerant from your system to bring the system back into the proper range. Never vent A/C refrigerant into the atmosphere. It is harmful to the environment and illegal to do so.
Refrigerant and the additives that accompany A/C Pro® products do not expire or 'go bad.' You can purchase or store an older generation can of refrigerant with the confidence that its contents are just as capable as a newly-packaged product.
The most common reasons the pressure gauge indicates a red/high pressure reading are either that the car is not running or the A/C is not on with the fan set to its highest setting and the A/C temperature set to its coldest setting. To obtain an accurate pressure reading, the car must be running with the A/C set to its coldest and the fan set to its highest. Also, as the car's compressor cycles on and off, the needle on the gauge may move in and out of the red/high pressure area of the gauge. This is normal.
If your vehicle's A/C isn't blowing cold it is likely low on refrigerant due to a leak. Most leaks are in rubber components such as O-rings, hoses, and gaskets.
The best way to find leaks is with our R-134a UV Leak Detection Kit (part # 436) which provides UV dye, high-intensity UV light and yellow tinted protective glasses.
Yes. The dye will not affect A/C performance.
Yes, the dye will continue to work the same way.
The leak sealer will take effect within 1 day of installation.
It of course depends on the nature of the leak, but typically leaks are sealed for approx 12 months of A/C usage.
They seal small holes that leak less than one can per month.
Your system will leak less refrigerant than it did previously. You cannot find a leak with the UV light that was there previously. Your system continues to blow cold air.
You should seek professional help.
Please click here to view the specifications by vehicle make.
Please see out dedicated page for R-134a and R-yf System Pressure Charts.
Need help finding your low side port? Use our Low Pressure Port Finder.
Universal gauges never require a DVA-1.
Self-sealing valve gauges never require a DVA-1.
You will need a DVA-1 when using these R-134 products:
ACP-101V
ACP-102V
ACP-102CA
ACP-105CA
ACP-307V
ACP-307CA
MRL-3V
You will need a DVA-1 when using these R-134 products:
ACP-101V
ACP-102V
ACP-102CA
ACP-105CA
ACP-307V
ACP-307CA
MRL-3V
You will need a DVA-1 when using these R-134 products:
ACP-101V
ACP-102V
ACP-102CA
ACP-105CA
ACP-307V
ACP-307VA
MRL-3V
For retrofitting and top-offs, use products that include Polyol Ester oil. When rebuilding a system that has been opened and flushed, use a pourable PAG oil of the viscosity that is recommended by the compressor manufacturer.
When an A/C system leaks refrigerant, some oil escapes also. Our products all have the proper ratio of oil to refrigerant already blended to replace the lost oil.
Hybrid vehicle A/C systems use a special oil with electrically insulating properties is used to keep voltage from leaking to the compressor case through the oil. According to the hybrid manufacturers, if even a small amount of another (i.e., the incorrect) oil is introduced into the system, it may significantly decrease the electrical insulation properties which can cause compressor damage. The introduction of the wrong oil can cause a diagnostic trouble code to trigger which may disable the air conditioning system.
Hybrid vehicle manufacturers also warn that if the wrong oil is introduced into and subsequently circulated through the system, all of the main A/C system parts (such as the evaporator, condenser, receiver/dryer, and compressor) should be replaced. It is recommended that a dedicated manifold gauge set be used when charging the system to ensure that any residual refrigerant oil left in the manifold gauges from refrigerant recovery on other vehicles does not enter the air conditioning system and deteriorate the insulating performance of the special oil.
One can of Super Seal is all you need to seal pin hole sized leaks in your system. In order to determine the size of your leak use the following rule of thumb: your car must be able to hold a refrigerant charge for at least two weeks. If you car can hold a charge for two weeks before blowing warm again, then Super Seal will be able to patch your leak. If you have a large hole or leak using two cans of Super Seal will not help.
Yes. The sealant technology in Super Seal has been used for decades in the underground gas transfer industry, sealing leaks in pipes, tanks, compressors, and other gas filled containers.
No! The chemical formulation in A/C Pro® Super Seal remains in a liquid state inside of the A/C system until it detects moisture at the leak point and self-seals. A/C Pro® Super Seal contains a drying agent to prevent any sealing activity while in the system and will be removed from the system along with the refrigerant should it ever leak out of be removed/evacuated.
Super Seal has a lower boiling point than the refrigerant oil. This enables the Super Seal to be removed from the system as the refrigerant either leaks out or is removed.
A/C Pro® Super Seal will repair most leaks in automotive air conditioning systems. However, the general rule is that if the system cannot hold a charge for 24 hours, the leak is too large and probably needs manual repair. If the system is leaking slowly and holds a charge for more than two weeks, A/C Pro® Super Seal should seal the leak. A/C Pro® Super Seal can seal multiple holes in both the metal and rubber parts of the A/C system and is an inexpensive alternative to having a mechanic work on the car, which could cost well in excess of $1,000.
Super Seal has sealed leaks in over 1,000,000 vehicles since its introduction in early . This moisture activated sealant technology has long been used in the gas transfer industry, sealing leaks in pipes, tanks, and other gas filled containers.
While in the air conditioning system, it remains a liquid lubricant and contains additives to penetrate and rejuvenate o-rings, gaskets and other rubber connectors to prevent leakage. Included in Super Seal is a drying agent that gets rid of any moisture that may be inside the air conditioner. If the refrigerant leak occurs in a metal part, the refrigerant leaves the system and chills the outside air causing condensation. This moisture activates the Super Seal fluid to form a scab on the exterior of the metal.
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