Automotive AC Pressure Chart

In today’s article, we will discuss the automotive AC pressure chart. A car’s air conditioner helps regulate engine temperature. For maximum fuel efficiency and minimum emissions. Proper use of car air conditioning is essential. Otherwise, you will face the problem of reduced fuel mileage. And may experience excessive stress on the engine. Your car’s AC pressure will tell you everything about your air conditioning system.

Car AC pressure Chart

High-Side and Low-Side

Want to understand the performance of your car’s air conditioning system? That’s why you need to measure high-side and low-side AC pressure. A pressure gauge with a small refrigerant characteristic may display low-side pressure. Low-side pressure gauges are inexpensive to manufacture. It is also easy to identify. They measure low pressure. So they don’t need to be specific. We will know about the automotive ac pressure chart.

The Right AC Pressure in Your Car

Higher-side pressures require an improved gauge and different connections. That’s because it’s hundreds of PSI higher than the low-side pressure. Your car’s air conditioning system needs an AC gauge set. Which measures high-side pressure. The AC gauge sets a gauge for high-side and low-side pressure. It comes with sight glass and a line to connect the system to a refill can.

This helps monitor the condition of your refrigerant. Like your engine oil dipstick. There is a range of low- and high-side pressures. It is acceptable and varies depending on the ambient temperature. However, typically, your low-side pressure should be 30 to 40 PSI. And the high-side pressure should be 150 to 175 PSI. Everything in your air conditioning system should be working normally. If the low-side and high-side pressures are within range, Also check your ventilation system for operational faults or condensers.

If you get low pressure on both sides of your air conditioning system, You have to add refrigerant. If you find high pressure on both sides of your system, But you can add too much refrigerant. A faulty compressor can be a problem. If your low-pressure gauge reads high, And your high-pressure gauge reads low. If your low-pressure gauge reads low, And if the high-pressure gauge reads high, Blockage of the expansion valve tube can cause problems. And an automotive ac pressure chart is useful for car ac.

How do I use an Automotive AC pressure chart?

If your car’s AC is not cooling properly, then it’s time to take your car to an AC technician. The first thing he would recommend is to check the refrigerant pressure. According to the car automotive ac pressure chart:

Whether pressure readings on both the high and low sides are within limits.

automotive ac pressure chart

A/C pressure chart

It is for checking the low side pressure and high side pressure of the refrigerant. A special testing device consists of two pressure gauges. Attached to the manifold assembly. The high-side pressure gauge and its connecting pipe are usually red in colour. The lower side pressure gauge and its connecting pipe are coloured blue.

Ac pressure chart image

The table below shows the automotive ac pressure chart for R134A refrigerant. This AC pressure chart contains R134a refrigerant values at room temperature. Where all the high- and low-side pressure values are.

How does car AC work?

How does your car’s air conditioning system work? Let’s have a basic overview. The process of removing heat from an area is called refrigeration. Unwanted heat is mechanically transferred to an external area. Where heat is objectionable.

An example of this system is:

Refrigerators and air conditioners.

Refrigerant is a special liquid called refrigerant. And used in air conditioners. It is a high-pressure fluid state. And facilitates heat transfer in a low-pressure gas state. When the process runs. It then absorbs heat and moisture from the car’s cabin. And provides cool and dry air.

All elements, viz.,

  • Compressor
  • Condenser
  • Accumulator and Evaporator

These elements will give you cold air. That’s why compatibility works. It is important for refrigerants to have certain properties, such as:

  • It should not be explosive or flammable.
  • It should have a low boiling point.
  • It should be non-corrosive to metal.
  • It should mix well with the oil.
  • It shouldn’t be dangerous.
  • Must be safe and non-toxic.
  • It has a large latent heat value.
  • It should be easy to liquefy or evaporate.

Its pressure and temperature should also be moderated. These are the properties a refrigerant must have. Even at the molecular level, there are certain requirements. Some popular refrigerants based on this characteristic are:

  • GHG-HP
  • hot shot
  • Icon-12
  • R-406a
  • R-12
  • R-134a
  • Freeze-12

R134a refrigerant

R-12 is also sold under the brand name Freon-12. Used as the main refrigerant in automobile and household refrigeration. But it has harmful effects on ozone. Due to this, it was banned in 1994.

Since R134a refrigerant is used in automotive AC pressure, It has become the industry standard in refrigeration and freezing applications. R134a has the same thermodynamic properties as R-12. But it has less impact on ozone layer depletion.

At atmospheric pressure, R134a has a boiling point of -26.8 oF, and the boiling point rises to -10.6 oC at a pressure of 10 psi. R134a is released into a room at atmospheric pressure and room temperature. But it will immediately turn into gas.

There is a direct relationship between these two. Temperature and pressure of the refrigerant. If the pressure of the refrigerant (R134a) is 35 psi, then its temperature will be 4.4 oC. Therefore, temperature and pressure play an important role. In the condensation and expansion of R134a.


R134a pressure chart 

Ambient temperature  High- side pressure  Low-side pressure 
65°F (18°C) 135-155 psi/ 931-1069 kPa 25-35 psi/ 172-241 kPa
70°F (21°C) 145-160 psi/1000-1103 kPa 35-40 psi/ 241-276 kPa
75°F (24°C) 150-170 psi/ 1034-1172 kPa 35-40 psi/ 241-310kPa
80°F (27°C) 175-210 psi/ 1207-1448 kPa 40-50 psi/ 276-345 kPa
85°F (29°C) 225-250 psi/ 1551-1724 kPa 45-55 psi/ 310-379 kPa
90°F (32°C) 250-270 psi/ 1724-1862 kPa 45-55 psi/ 310-379 kPa
95°F (35°C) 275-300 psi/ 1896-2068 kPa 50-55 psi/ 345-379 kPa
100°F (38°C) 315-325 psi/ 2172-2241 kPa 50-55 psi/ 345-379 kPa 
105°F (41°C) 330-335 psi/ 2275-2310 kPa 50-55 psi/ 345-379 kPa
110°F (43°C) 340-345 psi/ 2344-2379 kPa 50-55 psi/ 345-379 kPa

Interpret the pressure reading

High side pressure  Low side pressure  Action is required 
Within limits Within limits A/C is working properly 
Less Less Refrigerant must be added
High High Service required, possible blockage of expansion valve or orifice tube
Less Less Needs service, possibly faulty compressor
High High System overcharge

Normal operating pressure for R134A

The air conditioning refrigerant used in new automobiles is R134. The optimum running pressure will be 22 to 57 pounds per square inch.

According to the US Environmental Protection Agency,

A liquid capable of evaporating at low temperatures. That is used in air conditioning.

As a refrigerant states that,

R134A is not flammable at ambient temperatures. Non-corrosive to metals such as aluminum, copper, and stainless steel.


A general overview of the automotive ac pressure chart is necessary. Car AC pressure systems use R134a refrigerant. and automobile AC pressure charts for R134a. Your car’s AC system needs proper care and maintenance. Expect a long working life from it. Without any major repairs or installations. We suggest you visit a trusted AC technician or workshop. Check the high- and low-side pressure of the refrigerant frequently. This is good advice.


What is the volume of R134a gas?

The specific volume of refrigerant-134a is 0.01343 m3/kg.

How much pressure is normal in AC?

Most technicians in the HVAC field know the normal range of operation. It ranges from about 60 PSI to 85 PSI for R-22 and 105 PSI to 143 PSI for R-410A and is dependent on operating conditions.

How much refrigerant should I add?

Most cars hold 28 to 32 ounces of refrigerant. But larger vehicles and cars with rear A/C will likely have more. Check your vehicle manual for specific vehicle system capabilities.

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