How To Recharging Your Car’s Air Conditioning System

Cooling System

By Rodney (Mechanics)

If your air conditioner isn’t cooling properly due to low refrigerant, simply adding more refrigerant should fix it. You can usually do this yourself with a few cans of refrigerant and a simple hose connection.

First, you’ll need to identify the type of refrigerant your vehicle needs:

For passenger cars and light trucks made from 1995 to about 2015, you’ll typically use R-134a. It’s crucial not to use any other kind of refrigerant for these vehicles. Check the A/C information decal under the hood to confirm your system uses R-134a.

Starting around 2014-2015, more vehicles began using a different refrigerant known as R-1234yf. For these models, only use R-1234yf, never R-134a.

For most cars and light trucks made in 1994 or earlier, the original refrigerant was R-12. R-12 isn’t available for DIY use anymore, although some lower-quality R-12 might still be around. If these older vehicles need refrigerant, they can be filled with recycled R-12 from other old cars (a job for a professional repair shop), or with an alternative refrigerant, or even with R-134a with some adjustments.

CAUTION: Do not mixing different refrigerants. Keep using the same type that’s already in your system, unless you’re switching an old R-12 system to R-134a or another type.

WARNING: Using flammable refrigerants is against the law. Never use any refrigerant that’s flammable, like propane, butane, or other flammable hydrocarbons.

Where to Find Your High and Low Service Fittings

Now, locate the AC system’s service fittings. There are two: a HIGH and LOW side fitting. The HIGH side fitting is on the line from the compressor to the condenser, while LOW side fitting is typically on the suction hose or line from the accumulator to the compressor.

For older R-12 systems, the HIGH and LOW pressure service fittings have screw-type Schrader valves. On R-134a systems, the HIGH and LOW side service fittings use quick-connect style fittings. The low-pressure fitting is of smaller size compared to the high-pressure fitting. Late model vehicles with R-1234yf also have their own unique service fittings that differ from R-134a or R-12 systems.

High Low Pressure

Standard Operating Procedure for Air Conditioning Recharge

  1. First step, ensure you have the right refrigerant for your vehicle. Use R-134a for R-134a systems and R-1234yf for newer R-1234yf systems exclusively. Never mix different types of refrigerant. At this point, you can attach the charged connection hose and valve to a refrigerant can.
  2. To rupture the can’s top, turn the service hose valve.
  3. Gently rotate the valve to let out a small amount of refrigerant into the hose. This removes any air from the hose (which shouldn’t enter your A/C system).
  4. First, close the valve to prevent any more refrigerant from escaping. Then, swiftly attach the other end of the service hose to the LOW pressure service fitting on the A/C system.Be cautious: NEVER connect a refrigerant can to the HIGH side service fitting. The pressure inside the A/C system during operation might exceed the can’s burst strength, leading to an explosion! This should be impossible since the service hose for A/C recharging will only fit the smaller LOW pressure service fitting. Nonetheless, it’s crucial to be aware of the danger.
  5. Keep the can UPRIGHT to avoid liquid refrigerant entering the service hose. Only vapor should enter the A/C system (the compressor could be damaged if it takes in liquid!).
  6. OPTIONAL BUT STRONGLY SUGGESTED: Utilize a gauge to monitor the recharging. While not mandatory, a gauge aids in accurately recharging the A/C system, reducing the risk of undercharging or overcharging (both of which reduce cooling effectiveness).You can connect a high pressure A/C gauge to the HIGH pressure service fitting, a low pressure A/C gauge to the LOW pressure service fitting, or attach gauges to both fittings (this is what professional technicians do).

    NOTE: Some do-it-yourself recharge kits include a low-pressure gauge on the service hose or a can dispenser with a trigger-grip style. The gauge may feature different color-coded zones for various refrigerants. Ensure you’re checking the correct pressure range for the refrigerant type you’re using.

  7. Start the engine and set the A/C to MAX/HIGH.
  8. Caution: Insufficient refrigerant may prevent the compressor from activating. The low-pressure cutout switch is designed to halt compressor operation in such cases, safeguarding it from potential damage due to inadequate lubrication. Since the compressor must run to draw refrigerant through the service hose into the system, if it fails to engage when the A/C is activated, supplying battery voltage directly to the compressor clutch via a fused jumper wire may be necessary. Locate a single wire connector near the front of the compressor, disconnect it, and connect a jumper wire to the battery’s POSITIVE terminal. This action should engage the clutch and initiate compressor operation.
  9. Turn the valve on the service hose to allow refrigerant vapor to flow from the can into the A/C system. It might take over 10 minutes per can to transfer all the refrigerant into the A/C system. Recharging is faster in hot weather than cooler weather. Check the air from the A/C ducts inside the vehicle; it should be getting cooler.
  10. For a high or low pressure gauge (either one and even both) check the gauge(s), while recharging.For the LOW pressure gauge: If the reading is between 25 and 40 psi while the A/C is on, stop. The unit is fully charged and is working efficiently in line with our expectations. Refrain from putting more refrigerant. If the indicator is surpassing more than 50 psi, you’ve surely poured too much refrigeration into your air conditioning system. If your gauge is color-coded which have zones of three different refrigerants type which includes R-12, R-134a and/or R-1234yf, make sure you are within the right range for refrigerant that you are using.

    For the high pressure gauge: When the reading rise to about 200 to 225 psi (for R-12) or 225 to 250 psi (for R-134a), stop. The system is fully charged and should be cooling properly. Do not add more refrigerant.

    NOTE: High and low pressure readings vary depending on the system and outside temperatures; higher temperatures result in higher system pressure readings.

    Check the vehicle manufacturer’s specifications to learn and understanding the normal/typical operating pressures of the system and its total refrigerant capacity. Newer passenger car air conditioning systems typically contain a small amount of refrigerant, ranging from 14 to 28 ounces, so be cautious not to overfill if the system is low. Typically, one can of R-134a contains 12 oz. of refrigerant.

  11. If the system still requires more refrigerant after adding one can, add second can it okay. Close the valve on the service hose, disconnect the hose from the empty can, attach a new can to the service hose valve, turn the valve to puncture the new can, then fully open the valve so refrigerant can flow into the A/C system.

Once done, turn off the engine. Close the valve on the refrigerant can before disconnecting the service hose from the LOW pressure fitting (to prevent any remaining refrigerant from escaping). To prevent releasing any remaining refrigerant from the can, it is advised to keep the service hose attached to the can with the valve closed for future recharges.

Remember to reinstall the plastic caps on the service fittings and remove the jumper wire from the compressor if you used one to activate it.

R134a AC charge

Troubleshooting A/C System: Cold Air Disruption Diagnosis

If your A/C stops blowing cold air days, weeks, or months after you recharge it, there’s likely a leak causing the refrigerant to escape. Add leak detection dye to find the leak and repair it before recharging the system to avoid wasting time and effort.

New Regulations Governing R-134a Sales as of January 2018

New regulations apply to those who sell or distribute refrigerants for vehicle use, specifically concerning R-134a and other substitute refrigerants sold after January 1, 2018. These rules include certification requirements for buying large refrigerant containers and the inclusion of a self-sealing valve in small containers.

Under these regulations, anyone purchasing a substitute refrigerant for R-12 in containers larger than two pounds must show evidence of having a Section 609 Technician Certification. If the purchaser isn’t certified and is buying the refrigerant for a service facility, they must provide evidence that one or more technicians at the facility are certified.

Refrigerant wholesalers must keep records of sales including the purchaser’s name, sale date, and quantity purchased. Although wholesalers aren’t required to confirm technician certification, the EPA recommends that they obtain a statement certifying that the cylinders are intended for resale to certified technicians.

Individuals can buy small cans (under two pounds) of R-134a without certification. However, all cans produced after Jan. 1, must have a self-sealing valve to prevent refrigerant venting after removal from the charging valves. Retailers are allowed to sell their existing inventory of small cans without self-sealing valves as long as they were purchased before Dec. 31, 2017.

Regulations on Refrigerant Venting in Vehicle Repairs

Under the former EPA regulations it was illegal for a person (professional or DIY) to do that. Refrigerant can’t be knowingly released into the air during vehicle servicing. The law further demanded that repair shops should have recovery machines for refrigerant. These systems were to be hooked up to a car before anything was opened for repairs, which could potentially for causing the refrigerant to flee into the atmosphere when the system was opened for replacement of the components. By doing so we prevented other atmospheric CFCs entering into the atmosphere from older refrigerants R-12. While the logic behind this makes perfect sense and is ultimately worth it, the rules regulated R-134a as well, which doesn’t have CFCs and is not a concern for ozone depletion. In the same manner, recovery of R-134a is also needed because it is a greenhouse gas like any other and thus contributes to climate change. EPA regulations also call R-1234yf to be recovered but the issue is not that clear as R-1234yf neither does away the ozone layer nor highly impacts on global warming.

DIYers without air conditioner refrigerant recovery machines should be able to release refrigerant without any guilt during a system repair. Many of them just dump it. In addition, if A/C system in your car is leaking, most of the refrigerant has already leaked out, and there is no more to be released.

The EPA has issued a new rule that changes its previous regulations on venting refrigerants during vehicle servicing. Previously, all refrigerants, regardless of containing CFCs or global warming gases, were banned from being vented. Now, while R-12 must still be recovered and not vented, it seems acceptable to vent R-134a and R1234yf during servicing without the need for recovery.

The new rule also removes previous requirements for leak inspection and repair for R-134a and R-1234yf due to the absence of ozone-depleting CFC chemicals in both.

The EPA also put out a suggestion for a new rule. It’s about adopting three technical standards from SAE International for A/C recovery and recycling equipment for R-1234yf. This new rule would make sure this equipment meets certain updated SAE standards. These standards are:

  • J2843 for equipment dealing with flammable refrigerants for mobile air-conditioning systems.
  • J2851 applies to equipment utilized for handling contaminated R-134a or R-1234yf refrigerant in mobile air conditioning systems., and
  • J3030 applies to automotive refrigerant recovery, recycling, and recharging equipment designed for both R-1234yf and R-134a.