AC Refrigerant R134a Pressure Chart You Need to Check

Car AC is not working well? Does your vehicle’s AC low-side pressure seem too high? Or are you in a dilemma with the correct pressure of the R134a refrigerant? Whatever the reason, this R134a pressure chart can certainly help!

After discovering the dangerous effect of CFC and HCFC refrigerant on Ozon layer, HFC refrigerants (hydrofluorocarbons) are now widely used in almost all cooling and air conditioning systems as well as in modern automobiles. And R134a is one of the most used and popular ones.

So, today, we will showcase the pressure chart for R134a for different ambient temperatures. And after going through the chart, you can be able to decide yourself whether your car’s AC system needs diagnosis.

R134a Pressure Chart High and Low Side

Okay, so we are talking about one of the most popular HFC refrigerants- R134a. And now we will not make you wait anymore and present the car AC pressure chart for R134a refrigerant, both high and low side pressure. But in case you need to check the temperature concerning different ambient humidity, you can check the complete car AC temperature chart applicable for almost all automobile AC systems.

For your information, the pressure in the chart below for different temperatures is shown in PSI(Pressure per Square Inch) and Kpa(KiloPascal).

Ambient TemperatureHigh Side Pressure (HP)Low Side Pressure (LP)
In Farhenheight (◦F)In Celcius (◦C)In KPaIn PSIIn KPaIn PSI

Note: The ambient temperature here is the outside atmospheric temperature.

So, How to Read This AC Pressure Chart?

Here, the first column is for ambient temperature in ◦F and ◦C. And for the pressure- here you get two readings –one for the LP (Low side Pressure) and one for HP (High side Pressure).

So, when you attach the pressure gauge to troubleshoot your vehicle’s AC, there will be two gauges- one for LP and one for HP readings.

Now, check the pressure for different temperatures from the above chart and find the standard pressure. If anyone’s (LP or HP) pressure reading shows too high or too little, there can be any issues with the refrigerant gas or the AC compressor system.

For example, if you found the LP or the HP higher than the standard, then the AC condenser might be at fault. Let’s help you out a bit more with a troubleshooting table for different faulty AC pressure readings. 

Low Side Pressure (LP)High Side Pressure (HP)Troubleshooting Tips
At RangeAt RangeNo Issue
HighLowThe compressor is at fault, or the condenser fan is clogged.
LowHighSystem blockage issue. Need servicing.
HighHighOvercharged! Need to vent some refrigerant.
LowLowLow refrigerant problem. AC system needs refrigerant.

Besides these issues, if you find the gauge showing the same reading on both LP and HP gauges, then either the expansion valve in the AC systems is not working well, or the compressor replacement is recalled.

Warning: Never vent AC refrigerant gas in the air. It’s illegal and strictly prohibited in the USA and many other countries.

What Are Normal AC Pressure for R134A?

If the AC compressor is running well and the AC system works properly, the normal AC pressure for R134A refrigerant should be between 22-57 PSI. Oh, you are confused with the LP and HP. Then, let me ease you with the info that it can depend on the temperatures, and you have already got that from the above chart.

Frequently Asked Questions (FAQs)

How much R134A do I need?

Well, it depends on your car and it can be found in your car manual. However, most of the modern cars’ AC system holds 14-28 Oz. of refrigerant coolant. And once can of R134a holds around 12 Oz of coolant.

What is high Pressure in AC?

The high side pressure of an AC system is the pressure created by compressing the low-pressure vapor from the evaporator. This high-side pressure is created at the compressor discharge side, where the low-side pressure is transferred. This high-side pressure is transferred to the condensation. Generally, 200 and 250 PSI of high-side pressure reading is considered normal, depending on the ambient temperature.

What is Low Pressure in AC?

The low side pressure of any air conditioning system is the pressure that starts at the expansion valve, creating a low-pressure refrigerant. And this low-pressure refrigerant goes to the evaporator, and after that, the heat from inside the vehicle is transferred to the AC compressor, which creates the high-side pressure. According to Car from Japan reports, 25 and 30 PSI of low side pressure is the normal AC pressure. However, it depends on the temperature, of course.

Goodbye for Now!

The shocking fact is that despite being a popular refrigerant, R134a is now blooming out with its adverse impacts on Earth. How?

Todays Home Owner report shows that recently, the EU has banned using the refrigerant R134a on modern cars after 2011 as it has been proven to play a significant role in global warming. But other countries are not following any such notice.

So, it’s better to be aware while venting it out!

However, we can say that we have been able to reduce your cause of tension and help you with the complete R134a pressure chart to troubleshoot your car’s air conditioning system. So, you can now check your AC pressure and find out the issue yourself if any arises.

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