What are normal AC gauge pressures when the system is running? Generally speaking, you want around 27-psi on the low side and 200 on the high side.
- When the engine is on and the AC is on high, low pressure readings should be around 30 psi and the high pressure side should be about 250 psi depending on your car. The correct reading will display once the clutch engages and the gauge stops cycling.
What is normal pressure for AC unit?
Most technicians in the HVAC field know the normal range of operation for the low-pressure side of an air conditioning system. This tends to be around 60 PSI to 85 PSI for R-22 and 105 PSI to 143 PSI for R-410A and is dependent upon operating conditions.
What should high and low side AC pressures be?
The pressure reading from the low side should be between 25 and 30 psi and the high side between 200 and 250 psi. But if you see the AC low side high, high side low, such as the low side is 100 and the high side is 150, there might be problems with any of the inner components.
What should the pressures be on a 134a system?
For normal running pressures in the R134a system, at the lowest temperature, the coil should run at 22 pounds per square inch that is 45-20, 25 degrees Fahrenheit. While at the highest temperature it should be 57 pounds per square inches that is 60-20,40 degrees Fahrenheit.
What should AC gauges read R22?
R22 gauge pressure is 10.9 bar or 158.2 psi. High side pressure typically varies by equipment and metering controls. Low pressure or suction side typically varies by equipment. Low-pressure refrigerant turns on the carrier HVACR at 50 psi (R22 pressure at 30 degrees) and closes at 100 psi (R22 pressure at 85 degrees).
What are the symptoms of an overcharged AC system?
4 Signs Of An Overcharged Air Conditioning System
- Higher Cost of Operation. An overcharged air conditioner system costs more money to operate, by decreasing overall efficiency.
- Sticky Indoor Air.
- Excessive Condenser Heat.
- Non-Functioning Air Conditioner.
What happens if AC pressure is too high?
When the pressure of the AC system is too high this might indicate a leakage or diminishing amount of refrigerant, both of which require immediate attention. If the AC temperatures are abnormally warm, this could indicate an issue with the compressor that might need repair or replacement.
How do I know if my car AC compressor is bad?
What Are the Signs and Symptoms of a Bad A/C Compressor?
- A Lack of Hot Air Being Released Outside.
- Loud or Strange Noises From the Unit.
- Failure of the Compressor to Turn On.
- Circuit Breaker Tripping.
- Leaks Around the Air Conditioning Unit.
- Warm Air Instead of Cool Air Being Delivered to the House.
- Reduced Airflow.
Normal AC pressure gauge readings
The gauge photos below depict standard auto air conditioning pressure gauge readings for a fully operating auto air conditioning system. It should be noted that the pressures displayed on the gauges correspond to the temperature of the surrounding environment at the vehicle. It is assumed that the engine is running at 1,500 RPM and that the AC is on with the compressor working in order to obtain the standard pressures. Generally speaking, you want a low pressure of roughly 27 psi and a high pressure of around 200 psi.
See also: Normal AC pressure gauge readings?
Why 27-psi on the low side?
In an R-134a air conditioning system, 27-psi. on your gauge indicates that the refrigerant will create around 32°F at the evaporator (as long as the orifice tube/expansion valve is functioning correctly and there is no air in the system artificially inflating the pressure to 27-psi.). The temperature of water is barely below the freezing point at that position. R-134a pressures are typically 2.2 to 2.5 times higher than the ambient temperature entering the condenser, which is considered excessive.
At 200-psi, the refrigerant entering the condenser will have a temperature of around 130°F.
Normal high and low AC pressure gauge readings and ambient temperature pressure chart
Temperature of the surrounding environment in degrees Fahrenheit The readings from the low side pressure gauge and the readings from the high side pressure gauge 65°F Low side pressure (25-35 psi) is present at the ambient temperature. High side pressure (between 135 and 155 psi) 70°F Low side pressure (35-40 psi) is present at the ambient temperature. Side pressures of 145-160 psi are common. 75°F Low side pressure (35-45 psi) is present at the ambient temperature. Side pressures of 150-170 psi are common.
- 85°F Low side pressure (45-55 psi) is present at the ambient temperature.
- 90°F Low side pressure (45-55 psi) is present at the ambient temperature.
- High side pressure of 275.300 pounds per square inch 100°F Low side pressures of 50-55 psi are typical.
- 110°F Pressure on the low side of the atmosphere is 50.55 psi.
- Rick Muscoplat posted a blog entry on
Gauge Readout Tool
When troubleshooting an air conditioner, the first tool to use is the gauge pressure. The following table lists seven different gauge readouts that you may come across. When diagnosing an air conditioner, use the Gauge Readout Tool either alone or in conjunction with the table of Gauge Diagnostics.
Gauge Readout Tool
Conditions that are considered normal The presence of air in the cooling system (insufficient suction) The expansion valve is not working properly.
Excess refrigerant is used. Intrusion of Moisture There is no circulation of refrigerant. Table of Gauge Data Summary Diagnostics
Normal Conditions
1 Room for the Atmosphere Temperatures ranging from 30 to 38 degrees Celsius (86 – 96 F) Engine speed of around 1500 rpm, which is approximately 75% of the rated engine speed Return to the top of the page
Air in cooling system (insufficient suction)
Pressure Variables Low-pressure range: 36 to 50 psi High pressure ranges from 284 to 356 psi. IndicationsBoth pressures are EXTREMELY ELEVATED The pipe on the low-side is not chilly. Causes Air in the system is the cause of the problem. Immediately shut off the system. Recharge the refrigerant system. Check the readings on the gauges. If the system is used for an extended period of time with air in it, the liquid tank must be changed. Return to the top of the page
Defective expansion valve
Pressure Variables Low-pressure range: 30 to 36 psi High pressure ranges from 313 to 327 psi. Indications Both pressures are EXTREMELY ELEVATED. Causes Charge of refrigerant that is not correct The expansion valve is not working properly. Installation of the temperature sensor was not done correctly. Remedy Check the amount of refrigerant in the system. Check the installation and insulation of the temperature sensor. Replacement of the expansion valve is recommended if the refrigerant charge is satisfactory and the temperature sensor installation and insulation are correct.
Excessive refrigerant
Pressure Variables Low-pressure range: 36 to 43 psi 327+ psi on the high side IndicationsBoth pressures are EXTREMELY ELEVATED Causes Increased pressure as a result of an excessive amount of refrigerant Inadequate cooling of the condenser Remedy Check the level of refrigerant in the system. Ensure that the condenser is clean. Examine and adjust the fan belt and/or the condenser fan motors, if necessary. Return to the top of the page
Moisture Intrusion
Pressure Variables Low-pressure range: 18 to 28 psi High-pressure range: 85 to 256 psi Indications The low pressure side alternates between being vacuumed and being under normal atmospheric pressure. Causes The expansion valve in the air conditioner has become clogged due to the accumulation of moisture in the system. Remedy Immediately shut off the system. Replace the receiver dryer with a new one. Recharge the system’s batteries. Return to the top of the page
Refrigerant does not circulate
Pressure Variables Low pressure range: 0 to -29.99 psi High pressure ranges from 71 to 85 psi. Indications The low pressure side transforms into a vacuum. As previously said, there is a lot of pressure. Frost or condensation on the front and rear pipe connections of the receiver dryer or expansion valve are signs of a faulty receiver dryer. Causes The air conditioning system gets clogged by pollution or ice. The AC system has been shut down due to a faulty expansion valve or temperature sensor.
Remedy IMMEDIATELY DISCONTINUE OPERATION Examine the area for pollution or ice.
If the expansion valve is not functioning properly, it should be replaced. Replace the receiver dryer with a new one. Refill the system with refrigerant to the right level. Hoses that are kinked should be repaired. Return to the top of the page
Summary Table of Gauge Diagnostics
The pressure on the low pressure side is TOO HIGH. When the high pressure side is excessively high, the low pressure side will often become excessively high.
| Cause | Inspection | Remedy |
|---|---|---|
| Defective Thermoswitch | The magnetic clutch switch turns off before the outlet air temperature is sufficiently low. | Replace the thermoswitch |
| Poor Expansion Valvetemperature sensor contact | The high and low pressure sides gauge pressures equalize when the magnetic clutch is turned off (within a short time duration) | Replace Compressor |
| Expansion Valve opens too far | Frost has adhered to the suction hose / pipe | Install the temperature sensor against the low pressure pipe and cover with insulating tape. |
| Clogged compressor suction filter | Compressor fitting is cool but the low pressure hose is not. | Remove and clean the filter. |
The pressure on the low pressure side is WAY too low.
| Cause | Inspection | Remedy |
|---|---|---|
| Insufficient Refrigerant | There is little temperature difference between the low and high pressure sides. | Repair any leaks and recharge the refrigerant to the correct levels. |
| Clogged liquid tank(receiver dryer, accumulator) | Considerable temperature difference between the inlet and outlet sides of the receiver dryer during operation. Also, tank may be frosted | Replace liquid tank (receiver dryer) |
| Clogged expansion valve | Expansion valve inlet side is frosted. Generally the low side pressure is near vacuum. | Replace expansion valve. |
| Expansion valve temperaturesensor gas leak(damaged capillary tube, etc.) | Expansion valve outlet side is chilled and low pressure side is LOW. | Clean or replace expansion valve. |
| Clogged or blocked piping | Low pressure readings decrease or a negative reading is shown. Indicates piping is clogged or blocked between the evaporator coil and the compressor. A frost spot may indicate the point of blockage. | Clean or replace piping. |
| Defective thermoswitch(cold control) | Evaporator is frozen showing ice along the face of the coil, not just frost on the manifolds of the coil. | Adjust temperature sensing tube to a cooler part of the coil or replace the thermoswitch. |
The pressure on the high pressure side is TOO HIGH.
| Cause | Inspection | Remedy |
|---|---|---|
| Poor Condenser cooling | Dirty or clogged condenser fins, Cooling fans do not operate correctly. | Clean and / or repair the condenser core / fans. |
| Excessive refrigerant | Verify by gauge reading | Utilize your refrigerant recovery equipment to capture excess refrigerant. Charge to the correct refrigerant levels. |
| Air in the system | Pressure is high on both high and low sides | Evacuate, vacuum and recharge with refrigerant. |
The pressure on the high pressure side is TOO LOW.
| Cause | Inspection | Remedy |
|---|---|---|
| Insufficient refrigerant | Little temperature difference between the low and high pressures. | Repair any leaks and recharge the refrigerant to the correct levels |
Diagrams: System Pressure Chart
Find out what an average A/C system looks like, as well as the compressor manufacturer and what the R-134a requirements are for your particular automobile in this fast video.
| R-134a TEMPERATURE PRESSURE CHART(Tabla de Temperaturas y Lecturas) | ||
|---|---|---|
| AmbientTemperature °F / °C(Temperatura Ambiental) | Low-Pressure Gauge(Puerto de Servicio del Ladode Baja Presion) | High-Pressure Gauge(Puerto de Servicio del Ladode Lado de Alta Presion) |
| 65°F (18°C) | 25-35 psi / 172-241 kPa | 135-155 psi / 931-1069 kPa |
| 70°F (21°C) | 35-40 psi / 241-276 kPa | 145-160 psi / 1000-1103 kPa |
| 75°F (24°C) | 35-40 psi / 241-310 kPa | 150-170 psi / 1034-1172 kPa |
| 80°F (27°C) | 40-50 psi / 276-345 kPa | 175-210 psi / 1207-1448 kPa |
| 85°F (29°C) | 45-55 psi / 310-379 kPa | 225-250 psi / 1551-1724 kPa |
| 90°F (32°C) | 45-55 psi / 310-379 kPa | 250-270 psi / 1724-1862 kPa |
| 95°F (35°C) | 50-55 psi / 345-379 kPa | 275-300 psi / 1896-2068 kPa |
| 100°F (38°C) | 50-55 psi / 345-379 kPa | 315-325 psi / 2172-2241 kPa |
| 105°F (41°C) | 50-55 psi / 345-379 kPa | 330-335 psi / 2275-2310 kPa |
| 110°F (43°C) | 50-55 psi / 345-379 kPa | 340-345 psi / 2344-2379 kPa |
| Ambient temp is the outside atmospheric temperature. |
| INTERPRETING PRESSURE READINGS | ||
|---|---|---|
| Low-PressureGauge | High-PressureGauge | ActionRequired |
| IN RANGE | IN RANGE | A/C is working properly. |
| LOW | LOW | Add Refrigerant. |
| LOW | HIGH | Need service, possible blockage of theexpansion valve or orifice tube. |
| HIGH | LOW | Needs service, possibly faulty compressor. |
| HIGH | HIGH | System is overcharged. Slowly removerefrigerant. Venting is illegal in USA. |
| It is illegal to vent 134a refrigerant into the atmoshpere. |
What are my A/C pressure readings telling me about my A/C system? – Buy Auto Parts
If you suspect that you have a problem with your air conditioning system but are unsure of which component is causing the problem, it is a good idea to connect your compressor to a pressure gauge to check its performance. A fully functioning A/C system should have a high pressure of 150 PSI and a low pressure of 30 PSI on the high side. Obviously, the most common problem that individuals have when their air conditioning system fails is that the air that comes out of the vents is not chilly enough.
- 250 PSI / 50 PSI = Overcharged system with no cooling provided by the condenser.
- There is a good chance that the expansion valve has been opened too wide (this will not be the case if your A/C system includes an orifice tube).
- There is a clog somewhere in your system, either before or after the expansion device, resulting in a 200 PSI / 70 PSI result.
- The evaporator, pipe, and expansion valve should all be checked to see where the problem is coming from.
- A leak anywhere in your system or a jammed expansion valve at 150 PSI and 10 PSI might indicate a problem with your expansion valve.
- 100 PSI /100 PSI = The compressor is not engaging because there is no power being supplied to it, or you have a burned coil in the compressor.
- More information on interpreting AC pressure readings may be found on our How To page dedicated to the subject matter.
Written byBuyAutoParts
View all of the posts made by BuyAutoParts.
AGCO Automotive Repair Service – Baton Rouge, LA – Detailed Auto Topics
| They refer to the gas in an air conditioner as refrigerant. Over time, refrigerant may leak, and low refrigerant is one cause for an air conditioner to stop cooling.Many other thingsalso cause the system to not cool. Without diagnosing the real problem, adding more refrigerant may destroy the compressor and worse. |
What to do when an air conditioner stops cooling
When an air conditioner stops operating or does not provide adequate cooling, we must determine the source of the problem. Finding the root of the problem is not difficult. We only require a few tools and a small bit of information to get started. We utilize a pair of gauges to verify the flow of refrigerant through the system. Understanding refrigerant gauges is simple if you follow a few simple guidelines. There are two major components to our automobile air conditioner. As explained in part one of this series, all difficulties will be caused by one of the two components.
- These components must operate together to keep the car cool.
- Electrical testing equipment is used to identify and diagnose electrical faults.
- What we really need is an explanation of how air conditioning works in order to go forward.
- To fully comprehend the system, we must first grasp the high and low pressure sides of the system.
- In a nutshell, the system has two sides: a high side and a low side.
- We use these forces as a guide to identify potential difficulties.
- When refrigerant is added to a system without first understanding the high-side connection, severe damage might result in the system.
- It is hard to determine the right charge level on these machines even with both gauges in place.
The only method to charge them is to remove the system and charge it with the appropriate amount of refrigerant. A professional to test and charge these systems is significantly less expensive than destroying a compressor and evaporator core as a result of an over charge.
Basic automotive air conditioner pressure testing
R134A is the most commonly used automotive refrigerant today. R1234YF is a fuel that may be found in newer automobiles, and it is expected to become increasingly prevalent in the future. It is not addressed in this post how to diagnose R1234YF systems because they are different. Although the pressure in older systems differs somewhat from that of R134A, the basics remain the same. R12 is used in older systems. A refrigerant gauge set will consist of two gauges for measuring refrigerant. Indicators on the left are indicated in blue, and they are used to read the low-side of the system.
- Attachment to the system is accomplished by the use of a blue and a red hose.
- The majority of R134A gauges include quick-connect fittings on the hoses that allow them to be connected to the proper port.
- The gauges should only be fitted or removed while the engine is not running, regardless of the setup.
- By purging the lines, you will be able to eliminate this air and keep it from entering the system.
- Any air in the system will be forced out of the hose by the pressure in the system.
- When using quick-connects, the hoses will seal when they are removed, and purging should not be necessary again in the future.
What is static pressure in the system?
The static system pressure can be measured prior to the vehicle being started up. The pressure in both gauges should be very close to being the same. The actual pressure will vary depending on the kind of refrigerant used and the temperature of the surrounding environment, and it will not indicate whether or not the system has been adequately charged. R134A has a pressure of around 90 pounds per square inch when heated to 85 degrees Fahrenheit. Readings that are significantly lower than expected indicate that the system is low on charge or polluted with air.
Finding and fixing leaks will be explored in further detail in the following Detailed Topic.
What is normal automotive air conditioner pressure?
The engine should be started, and the air conditioner should be turned on. Actual measurements will vary depending on the temperature of the environment. When the temperature is 90 degrees Fahrenheit or less, the low-side pressure should be about 30 PSI. When the pressure is abnormally low or high, it indicates that there is a problem. Ideally, the high-side pressure will be approximately twice the ambient temperature + 50 PSI in a well functioning system. For example, on a 90-degree Fahrenheit day, twice 90 is 180, plus 50 equals 230 pounds per square inch of pressure.
Given that both pressures are within these limits, the system should generate a vent temperature in the mid-to-low forties while running the engine idling at a constant speed.
A chilly line indicates that the problem is most likely under the dash, with the actuators or with the doors. When a temperature door fails, the cooled air can be forced back into the room. This is called reheating.
What does higher than normal air conditioner pressures mean?
Low and high-side pressures that are significantly greater than normal are quite harmful. Compressors for air conditioners are designed to work within a specific temperature range. Higher than usual pressure will deform the aluminum casing, resulting in the compressor failing in a short period of time. The coils in the evaporator will also leak as a result of the high pressure. This may be highly expensive, as it is typically necessary to remove the dash in order to rectify the problem. The lack of air movement through the condenser and the overcharging of the system are the two most common causes of greater than normal air conditioner pressures, respectively.
It is also possible that a worn fan clutch or dirt obstructing air passage through the condenser is causing the problem.
A condenser fan turning does NOT mean it is moving sufficient air
Many electric fans and clutches are capable of operating at various speeds ranging from 15 percent to 100 percent of their maximum capacity. A faulty module or sensor may cause the fan to turn too slowly, resulting in insufficient cooling of the condenser. The same is true for a fan clutch, which may function at a variety of speeds. It is advisable to leave the testing of air flow and fan speed to those who are well-versed in the procedure.
How does a system get overcharged?
It is possible to overcharge an air conditioner as a consequence of the addition of refrigerant, oil, or air that has remained in the system. Extracting the contents and measuring them is the only method to determine if there is an overcharge. Overcharging is frequently caused by adding extra refrigerant to a system without first determining why the system is not cooling properly. When a line on an air conditioner system is opened, air is allowed to enter the system and cool the room. The same thing might happen if the refrigerant seeps out and the system is completely depleted.
- Due to the fact that air takes up space, applying the appropriate charge results in an overcharge.
- Oil is used in a variety of components, including compressors, condensers, and accumulators.
- When there is insufficient oil in the system, the compressor will burn up.
- Oil takes up space, and adding it in a haphazard manner might result in an overcharged system after the right amount of refrigerant has been added.
Replacement compressors must also be drained and measured before they can be used. Many new compressors have more oil in them than was extracted by the previous one. This is a problem.
What does it mean when the low-side is high, and the high-side is low?
In order to remove heat from the car, the compressor reduces the low-side pressure and raises the high-side pressure. A broken compressor will not be able to make as big of a difference on both sides. While this occurs, cooling will be reduced, especially when the vehicle is at rest. It is possible that increasing the engine speed will bring the pressures closer to what is required. Compressors that operate in a clean and oiled atmosphere have a long life. If a compressor is malfunctioning, the fundamental cause must be identified, else the problem would return.
The low-side is way too low and the high-side too high
In most cases, insufficient low-side pressure on a fully charged system is the result of a restrictive component. A blocked orifice tube is a typical source of these types of issues. As the compressor tries to drive the refrigerant past the obstacle, the high-side pressure may become higher as a consequence. This will soon suffocate the compressor’s oil supply, resulting in a catastrophic breakdown of the machine. When imposing any limitation, it is necessary to take the source of the trash into consideration.
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Why would both gauges read low?
R134a Pressure Gauge Readings
HOW TO UNDERSTAND YOUR GAUGES If your employees are unable to read the gauges, they are unable to comprehend air conditioning. Despite the fact that this is a fundamental introduction to gauge reading, it is only applicable to the vast majority of cars; as such, it should only be used as a guide. Prior to testing, the vehicle should be recovered, cleaned, and charged to ensure that it is in good working order. If you are reading your gauges, there are a handful of fundamental factors that you should keep in mind — THE TEMPERATURE IN THE ROOM The system should be recovered, vacuumed (for a minimum of 20 minutes), and recharged after each use.
In summer, when the air conditioning is switched off, the pressure will be low, and on cold days, the pressure will be high.
TURN OFF THE AIR CONDITIONING
| AMBIENT TEMPERATURE (CELCIUS) | R134a PRESSURE (PSI) |
| 0 | 30 |
| 10 | 45 |
| 15 | 55 |
| 20 | 70 |
| 25 | 80 |
| 30 | 100 |
| 35 | 115 |
| 40 | 130 |
Pressure and temperature will vary in tandem; as one rises, the other will rise, and as one falls, the other will fall, as one rises, the other will fall. It is expected that different refrigerants would have varying numbers. Understand what normal gauge readings are and how they differ from one another. TURNING ON THE AIR CONDITIONING
| AIR TEMP (C) | RED GAUGE (PSI) | BLUE GAUGE (PSI) |
| 0 | 40-50 | 20-30 |
| 10 | 50-100 | 20-30 |
| 20 | 100-150 | 20-30 |
| 30 | 150-200 | 25-35 |
| 40 | 180-225 | 25-35 |
As the ambient temperature rises, the red gauge increases in pressure (from 40psi to 225psi), but the blue gauge remains at a constant low pressure (40psi) (20psi to 35psi). When the fan is activated, the red gauge stops climbing, which is normally between 180psi and 225psi. TYPE OF COMPRESSOR It will be described only the two most prevalent systems – manual air conditioning and automatic climate control – in order to keep things simple. MANUAL A/C – The compressor is either fully operational or completely inactive (the familiar clicking sound as the compressor engages).
When the pump is turned on and off, the gauge readings will be as shown above.
When it achieves the desired temperature it reduces the amount of refrigerant being forced through the system (there is no clutch plate to click on or off, it is internally regulated).
As previously stated, the gauge readings will be as follows initially; however, once the vehicle has reached the proper temperature, the compressor will begin to pump less refrigerant through the system.
When less refrigerant is being pumped, the pressure displayed on the red gauge will be lower than when more is pumped.
| AMBIENT TEMP | RED GAUGE (PSI) | BLUE GAUGE (PSI) |
| 0 | 30-40 | 20-30 |
| 10 | 40-60 | 20-30 |
| 20 | 60-120 | 20-30 |
| 30 | 120-150 | 25-35 |
| 40 | 150-180 | 25-35 |
When the appropriate temperature is attained in chilly weather, the red gauge will only slightly raise, giving the appearance that the compressor is not working, which is not the case. Illustrations of flaws
- If neither of the gauges moves, this indicates that the compressor is not pumping. Fuse, pressure sensor, fan belt slippage, relay, wire break, lack of gas, compressor failure are all examples of possible defects to look for. A high reading on the red gauge indicates that the compressor is pushing against a stalemate. This happens when there is a blockage on the suction side of the compressor (blue gauge), which causes the pressure to drop. Filter blockage, crushed pipe, too much gas/oil, and a clogged thermal expansion valve are all examples of possible defects.
As pressure increases, the temperature increases as well, which means that the pipes, filters, and other components will be HOT up to the point of the blockage and COLD (perhaps freezing) immediately following the obstruction.
- If the red gauge reads more than 225psi, check to see if the fan is operating properly. Possible fan switch failure
- This might be a single switch near the condenser or a combination of the fan switch and the pressure switch (assuming the pressure switch has four wires)
- The vehicle’s cooling system is inadequate. All of the foregoing are possible faults, as well as – condenser air flow restriction, vacuum duration that is too short, contaminated refrigerant (a/c unit that has not been serviced on a regular basis)
- If the red gauge is too low and the blue gauge is too high, the engine will overheat. Possibility of problem – the compressor has degraded to the point that it is unable to generate sufficient pressure on the discharge side (red gauge) or sufficient suction on the intake side (blue gauge)
Finally, if a system is turned off and has approximately 10% of its full charge remaining, as long as there is some liquid refrigerant in the system, the pressure gauges will continue to read the relevant pressure for the ambient temperature, i.e. 70psi at 20 C. However, when only vapour is present in the system, the pressure gauges will read a lower pressure. As a result, recover, vacuum, and charge at every opportunity.
R134a High and Low Side A/C System Temperature Pressure Chart
This chart shows how the ambient temperature connects with the refrigerant charge pressure in the system, as well as how it impacts the high and low side psi readings on the system. Recharging refrigerant or diagnosing an a/c system based on pressure readings from your gauges are also possible uses for this device.
| Ambient Temperature (°F) | Low Side | High Side |
| 110° | 50-55 psi | 335-345 psi |
| 105° | 50-55 psi | 325-335 psi |
| 100° | 50-55 psi | 300-325 psi |
| 95° | 50-55 psi | 275-300 psi |
| 90° | 50-55 psi | 250-275 psi |
| 85° | 50-55 psi | 220-250 psi |
| 80° | 45-50 psi | 175-220 psi |
| 75° | 40-45 psi | 150-175 psi |
| 70° | 35-40 psi | 140-165 psi |
| 65° | 25-35 psi | 135-155 psi |
A/C System Pressure Troubleshooting
This temperature and pressure relationship charge, when used in conjunction with a pair of high and low side gauges, may be utilized to diagnose an a/c compressor that is not functioning properly. There is insufficient refrigerant charge to meet manufacturer specifications on the low side and high side pressures. The air conditioning compressor is not engaged, and the variable displacement is not operational. Performance of the air conditioning compressor is degrading. Both the low-side and high-side pressures are elevated, and the refrigerant charge exceeds the manufacturer’s specifications.
Condenser is clogged and ventilation is obstructed.
Side Pressure is at a low level.
System constraint at a high level A/C compressor breaking internally due to pressures being equal or close to same The variable displacement feature of the A/C compressor is not operational.
Learn What Your Car AC Pressures Mean When Your Car Has No Cold Air
As a result, you will almost certainly require a set of pressure gauges in order to identify this ailment. It is also possible to adjust the temperature of a refrigerant by increasing or decreasing the pressure of the gas. If the pressure in any section of the system is not maintained at the desired PSI, the refrigerant may not get cold enough, or may not become cold at all. To acquire a more in-depth description of the gauges required to examine your system, please click on the image. Prior to starting the engine, you will need to check the pressures at idle, taking note of both the HIGH and LOW side pressures.
If any or both of these parameters are not met, check the choices below to begin looking into your situation in further depth.
H – too lowL – too low
System is either undercharged or has too much oil. Visually inspect the system for any leaks that may exist. If you are running short on refrigerant, it is likely that it has spilled somewhere. Extensive examination of the hose ferrules, fitting connections at the compressor, condenser, and evaporator or expansion device should reveal oil residue. After determining that there is no evident leak, collect the refrigerant and repair the service ports or valves, evacuate and recharge the system, and add dye in the event that a second leak is discovered.
- The release of R134A refrigerant into the environment is prohibited.
- *** A good vacuum pump should be used for evacuation, one that is capable of bringing the system down to at least 29.75 ‘hg (inches of mercury) or more and maintaining it at that level for a minimum of 30 minutes.
- This also guarantees that the system has been completely de-gassed of any remaining air.
- This implies that you should not utilize a can of refrigerant purchased from an auto parts store that just has one gauge on it, for example.
- You’ll need gauges, a vacuum pump, and a scale in order to do this properly.
- Once the vacuum is complete, let it to sit for approximately 5 minutes to observe if the vacuum pressure has been lost.
- If the leak down test is successful, proceed to add the exact amount of refrigerant required for your system, as well as some dye or oil.
- Only a tiny amount of oil combined with the color should be added during the service, or as near as possible.
- When you’re finished, start the vehicle while keeping the gauges connected and record the new pressures.
- If the wind is blowing chilly right now, step outside and enjoy the fresh air!
H – too highL – too high
System is either undercharged or has an excessive amount of oil circulating. Visually inspect the system to see whether there are any leaks present. A leak in the system is the most likely cause of low refrigerant levels. Extensive examination of the hose ferrules, fitting connections at the compressor, condenser, and evaporator or expansion device should be made for evidence of oil contamination. After determining that there is no evident leak, collect the refrigerant and repair the service ports or valves, evacuate and recharge the system, and add dye in the event that a second leak is detected.
- The release of R134A refrigerant into the atmosphere is strictly prohibited.
- *** A good vacuum pump should be used for evacuation, one that is capable of bringing the system down to at least 29.75 ‘hg (inches of mercury) or more and maintaining it at that pressure for at least 30 minutes.
- The removal of all air from the system is also ensured by this procedure.
- Using a can of refrigerant from an auto parts store that only has one gauge on it is not recommended.
- If you want to accomplish this right, you’ll need gauges, a vacuum pump, and a scale.
- Wait about 5 minutes after you’ve finished vacuuming to observe if the suction pressure has diminished.
- Adding the correct amount of refrigerant required for your system, as well as some dye or oil, will ensure that the leak down test is successful.
- A tiny amount of oil combined with the dye is all that should be used during the service, or almost all of them.
A cup of 5oz will be sufficient for this purpose When you’re finished, start the car while keeping the gauges attached and note the new pressures. If the problem persists, please return to the DIAGNOSING YOUR AIR CONDITIONING page. Take advantage of the chilly air if it is blowing cold right now.
H – OKL – too low
Frosting on the evaporator or a malfunctioning expansion valve. Some cars are equipped with sensors that can detect when the evaporator is becoming too cold, which can cause the refrigerant to essentially freeze inside the evaporator, blocking the flow of cool air and resulting in a loss of cooling capacity. Due to the fact that most automobiles do not have a monitoring system for this symptom, we must examine our tire pressures. It is quite likely that you have a jammed expansion valve if you find that the high side pressure is at the correct pressure but the low side pressure is extremely low or practically to a vacuum.
H – too lowL – too high
Low refrigerant levels or a failed compressor are common problems. While the gauges are attached, crank the engine to 2000 RPM and see what happens to the pressures in the air conditioning system. Does it appear that they are moving closer together (high side becomes lower, while low side gets higher) or that they are moving away from one another? If they begin to migrate away from one another, begin by emptying and recharging the system, followed by retesting. You have a weak compressor if they all move at the same time; thus, it is advised that you replace the system.
- Some cars, such as a large number of Fords and Chevrolets, will require the condenser and/or manifold lines to be replaced since the way they are built makes it impossible to flush junk from them.
- In certain systems, like as those used in many Hondas, the drier is integrated into the condenser.
- Refer to the section above for suitable technique.
- Make certain that this work is completed correctly.
- Keep in mind that every vehicle is unique, and there are a variety of regulating and monitoring equipment that might contribute to your air conditioning not functioning.
AC Pressure Chart
| Ambient Temperature (°F) | Low Side | High Side |
| 110° | 50-55 psi | 335-345 psi |
| 105° | 50-55 psi | 325-335 psi |
| 100° | 50-55 psi | 300-325 psi |
| 95° | 50-55 psi | 275-300 psi |
| 90° | 50-55 psi | 250-275 psi |
| 85° | 50-55 psi | 220-250 psi |
| 80° | 45-50 psi | 175-220 psi |
| 75° | 40-45 psi | 150-175 psi |
| 70° | 35-40 psi | 140-165 psi |
| 65° | 25-35 psi | 135-155 psi |
When you have confidence in your air conditioning compressor, it indicates that it is functioning at peak performance. However, because it is a component of refrigeration, it is susceptible to malfunctioning. If you find yourself in this circumstance, you will want the assistance of your air conditioning compressor unit. That is something that a competent technician can perform for you. The technician should be equipped with the appropriate tools and knowledge of the A/C compressor. One of the instruments required is a pressure chart, which serves as an informational tool.
Consider the following sort of pressure chart: the R134a low side pressure chart, which we’ll look at in this post.
Continue reading if you want to find out what an R134a low-pressure chart is. Before we explain the R134a low side pressure chart, it is important to understand what the abbreviation r134a means. So,
What does R134a mean?
R134a is a refrigerant that is utilized in a broad variety of household and industrial products. These household appliances are equipped with a refrigeration unit, which is referred to as a compressor. The refrigerant R134a is contained within this compressor. The refrigerant ensures that the compressor is able to fulfill its duties properly. The installation of a gauge or meter aids in the comprehension of the normal working of this component. The pressure measurements on the meter are shown in conjunction with the refrigerant’s temperature readings.
The readings are recorded on a table with three columns, which is shown below.
The table is referred to as the pressure chart in most cases.
The pressure-temperature relationship for R134a refrigerant is depicted on the R134a pressure chart.
- High side pressure chart for R134a and low side pressure chart for R134a
High side pressure chart for R134a and low side pressure chart for R134a are both available.
What is a R134a Low Side Pressure Chart?
Does the R134a low side pressure chart have any significance? It is a chart that details the relationship between pressure and temperature on the lower side of the air conditioning compressor. Yes.How? This chart is used by the technician to assess whether or not the A/C compressor need a refrigerant recharge. It also tells you whether or not the compressor needs to be replaced. As a result, it is used to assess the overall state of the A/C compressor system. The R134a low side pressure chart is used to determine whether or not the A/C compressor unit is functioning at its peak performance.
In a similar vein, interpreting the readings on the charts is never straightforward.
When interpreting this reading, you must compare both the low and high sides of the chart to determine what the reading indicates.
Keep in mind that we are comparing the measurement of pressure to the reading of temperature.
How to Read an R134a low Side Pressure Chart
Does the R134a low side pressure chart have any significance? It is a chart that shows the relationship between pressure and temperature on the lower side of the A/C compressor. Yes.How? This chart is used by the technician to identify whether or not the A/C compressor need a refrigerant recharge. It also informs you whether or not the compressor needs to be replaced. This chart is used to determine the overall condition of an air conditioning compressor system. The R134a low side pressure chart is used to determine whether or not an air conditioning compressor unit is operating at its maximum efficiency.
The interpretation of the reading on the charts is no less difficult.
As a result, you must be aware of what each reading implies.
However, the focus of this post is on the R131a low side pressure chart, therefore let’s concentrate on the values on the low side of the graph. Keep in mind that we are contrasting the reading of pressure with the reading of temperature.
- Pressure is low on the low side when contrasted to the high temperature on the high side. It should reveal two things to you:
- The air conditioning compressor system is not operational. Consequently, the displacement in its operation changes, and it is possible that the compressor’s operation is failing. As a result, you must replace it with another one.
- When the pressure on the low side of the chart is particularly high, keep an eye out for the following:
- The following indicators should be looked for when there is significant pressure on the low side of the chart.
- The low pressure and high temperature are depicted as a contrasting pair on the low side of the chart. When this occurs, it should indicate that the system is not working at maximum capacity. When you look at the R134a pressure chart, you’ll see that the pressure is about similar on both sides of the graph. Take into consideration the following:
- Temperature and pressure are in opposition on the bottom side of the chart, which is higher than normal. When this happens, it should indicate that the system is not running at maximum capacity. When you look at the R134a pressure chart, you will see that the pressure is about identical on both sides of the graph. Take the following into consideration:
In other words, it’s possible that the A/C compressor is experiencing internal problems. Wait a minute, I know you’re thinking and asking yourself, ‘What am I talking about?’
What are the Normal Operating Pressures for R134a?
The pressure for an R134a system that is normally in operation ranges between 22 and 57 pounds per square inch (PSI). You should keep in mind that there are two sides to the chart: the low and the high. Because of this, the low-pressure side should be 90 degrees or less in a standard R134a, and the PSI should be near to 30. You may still be perplexed after reading through all of the preceding information.
Why Is my Low Side AC Pressure High?
An R134a compressor that is normally in operation produces pressures ranging from around 22 to 57 pounds per square inch (PSI). Remember, there are two sides to the chart; we have the low and the high points of the chart. The low-pressure side should be 90 degrees or less in a typical R134A, and the PSI should be near to 30 in a normal R134A. You may still be perplexed after going through all of the information above.
- It is possible that the condenser fan is not operating owing to blocked dirt. In this case, there is a blockage in the passage of air
- The refrigerant may not be flowing adequately
All of the issues listed above may be identified by a competent individual using the appropriate techniques.
Conclusion
Every technician has to be familiar with the r134a low-pressure chart. Whether it is for a residential inspection and interpretation or a business interpretation, we can help. The table aids in the inspection, identification, and resolution of problems that may arise as a result of the readings. If you work as a technician, you should consider keeping it on hand at all times.
What Should my AC Pressure Be?
Identifying the pressures present in your car’s air conditioning system may provide nearly all of the information you want about how well your system is performing at any one time. AC pressure used to be difficult to measure and necessitated the use of expensive gear, but thanks to technological advancements and the assistance of local auto parts stores, measuring one component of your air conditioning system has become much simpler. AC refill cans are widely accessible at your local car parts store, as well as at many bigger retail establishments.
- Using one of these gauges to detect the low side pressure in your system might be a pretty precise and economical method.
- If you look at your air conditioning system from the perspective of pressure, it is divided in two.
- This is due to the fact that the can of refrigerant you got from the auto parts store is pressurized, allowing it to force additional refrigerant through the system.
- It takes a more sophisticated piece of equipment to measure the pressure on the high-pressure side of your system.
- Get the right tools for your system from your local auto parts store if you want to measure the high-pressure side of it the most accurately.
- Now that you’ve discovered a safe and dependable method of measuring your air conditioning pressure, you’ll need to know what to look for.
- The greater the pressure will be outside, the warmer it will be outdoors.
- Because leaks are a prevalent problem in automotive air conditioning systems, if you notice that you have low pressure on the low side of your system, it is most probable that you have a leak.
- You may have an overfilled system if you have just added refrigerant, which might indicate a malfunctioning compressor.
- A low pressure on the high-pressure side of the system can also indicate that you have a low refrigerant level, or if the pressure on the high-pressure side is almost the same as the pressure on the low-pressure side, it can confirm that you are experiencing compressor problems.
- In order to fix the majority of air conditioning system issues, a vacuum, repair, and refill of the system are required.
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66 responses to ‘What Should my AC Pressure Be?’
When it comes to automotive systems, the air conditioning system is one of the most picky things you can find. Many issues might arise, ranging from air conditioning that does not function at all to air conditioning that operates either partially or not at all. This is something that many drivers are willing to overlook for the time being because air conditioning is not necessary for the correct operation of a car. A common problem that occurs with air conditioning systems is when the pressure onthe low side of the compressor is too high while the pressure onthe high side of the compressor is inadequately high.
The temperature that your air conditioning system is capable of producing is directly proportional to the pressure that exists throughout the system.
Additionally, you may seek up the recommended temperatures and refrigerant pressures that are necessary for the specific type of air conditioner installed in your car.
How to Check your AC Pressure
The process of determining the pressure in your air conditioning system is not complicated. All that is required is that you connect a gauge set to the air conditioning system and record the pressures on both the low and high sides. If you want to do this yourself, you can purchase an air conditioning pressure gauge on Amazon for approximately $30 or so. Some of them can be quite a bit more expensive, but if all you’re doing is monitoring the pressure, that should be plenty to get the job done for you at a reasonably low cost.
If the pressure on the high side and the pressure on the low side are the same as the pressure recorded for the ambient temperature surrounding your air conditioner, then you do not have an issue with the pressure of your cooling fluid.
Having 0 pressure suggests that you have no coolant at all, and it’s probable that it’s leaking completely from somewhere.
What Should the Pressure of your AC System Be?
As we’ve established, your air conditioning system has two distinct sides, each of which has a different level of pressure. When you connect the gauge to your air conditioning system in order to measure the pressures, the gauge should give you a number that is somewhere between 25 pounds per square inch and 30 pounds per square inch on the low side. That’s approximately normal for the low pressure, and it will only vary a small amount depending on the temperature of the air around your engine compartment during operation.
If both of your figures fall within these limits, then everything is functioning as it should, and you shouldn’t have too many concerns regarding your air conditioning system at this time.
If nothing else, you have eliminated this issue as the source of your problem, so it isn’t wholly a waste of time to investigate it further even if it isn’t the problem that you are experiencing.
What Happens if the Readings Aren’t Normal?
If you find that when you measure the pressure on the low side of your air conditioner, it rises above 100, while the pressure on the high side drops to around 150 or lower, you have a problem with the low side being high and the high side being low, you have a problem with the low side being high and the high side being low. Obviously, this indicates that there is a problem with the air conditioning machine itself, which is causing this to malfunction.
What Causes High Pressure When the Engine is Off?
If the air pressure in your system is greater than normal even while the engine is operating, it might be a sign of one of two things: one of the problems listed below. Problems with the condenser fan: Your condenser fan motor may be malfunctioning due to dirt obstructing the airflow, or the motor may have been damaged in some other way. This will restrict the airflow through the condenser, which will result in the condenser being unable to adequately cool the air conditioning system. When the condenser fan is subjected to excessive pressure, the metal can bend, resulting in leaking from the evaporator coil and other problems.
System that has been overcharged: It is also possible that you are feeling high pressure even when the motor is turned down due to the fact that your entire air conditioning system has been over charged.
In order to relieve the strain, it’s important to enlist the help of an experienced technician who can do the task safely and correctly.
If the pressure is high while the machine is working, it’s possible that this is merely part of the routine operating operation.
What Causes Low Side Pressure to Go Too High?
It’s likely that you’re experiencing condenser problems if you notice that the low side pressure is greater than it should be while the high side pressure is approximately normal. For your air conditioning system to function effectively, your condenser must go through a series of cycles. Consequently, if the condenser completes this cycle more quickly than it is meant to, the pressure on the low side will rise more rapidly than is normally expected to occur. This might be the consequence of a problem with your thermostat switch or temperature gauge, but you’ll need to take your vehicle to a repair to get a clear diagnosis on this.
What Causes the Low-Pressure Side to Go Too High and the High Side Pressure to Go Too Low?
Although there are a variety of factors that might cause your low side pressure to become too high and your high side pressure to become excessively low, when both of these conditions occur at the same time, you have a limited number of alternatives. If you use your gauge and establish that your low side is higher than 100 and your high side is lower than 150, the chances are good that a mechanic will inform you that the problem you’re experiencing is a compressor failure.
In addition, it’s likely that you’re experiencing difficulties with your pressure switch, expansion valve, or receiver/dryer.
What is a Car’s AC Compressor?
The compressor is the component of your vehicle’s air conditioning system that is responsible for creating the pressure that the coolant is forced to operate under. If there is a problem with the pressure in your air conditioning system, this would be the first place to examine. In order to maintain pressure on both sides of the compressor, it must first rise pressure before passing through your air conditioning system to the condenser, where it converts from a gas to a liquid, and then drop pressure while the cooling process occurs.
If your compressor is not operating in the manner in which it is meant to, the pressure in your air conditioning system will most likely be significantly impacted as a result.
What is the Pressure Switch in My Car’s AC?
If it is not the compressor that is producing problems with your AC pressure, it is possible that the pressure switch is to blame. Located on both the high and low sides of your air conditioning system, the pressure switch monitors the pressure of the refrigerant as it passes around the system. The purpose of the switch is to shut down the compressor in order to prevent harm if the pressure becomes too high for the system to withstand. If the switch does not function properly, this will not be able to occur, and your pressure will be thrown out of balance as a result.
What is An Expansion Valve in My Car’s AC?
Another factor that can cause the pressure on the low side to become excessively high and the pressure on the high side to become excessively low is the failure of the expansion valve. Your expansion valve is placed near the evaporator and is responsible for regulating the flow of refrigerant throughout the whole air conditioning system. If there is too much coolant flowing through the system, the system may freeze, and if there is not enough, the evaporator may overheat and cause damage to the system.
It is possible to have the fluid levels thrown off if the expansion valve malfunctions.
What is the Receiver/Drier in My Car’s AC?
The receiver/dryer is a component of your air conditioning system that stores and dries the refrigerant used in the air conditioning. It contains something known as a desiccant, which is comparable to those small packets that you would find in a new pair of shoes or other items that are intended to keep the wearer’s feet dry. They are often labeled with a warning that they should not be consumed. The desiccant in your air conditioning machine performs the same function. It draws moisture from the refrigerant and absorbs it, preventing the refrigerant from becoming polluted with water.
If you have an excessive amount of water in your system and the receiver / drier is overloaded, it will be unable to perform the functions it is designed to perform.
That in turn can cause issues with your air conditioning compressor and expansion valve as well as the problem of your low side pressure being too high and your high side pressure being excessively low.
The Bottom Line
The pressure gauge that we referred to above is the most accurate way to determine if you have an issue with the low side of your air conditioner being too high and the high side being too low. That way, you can at the very least determine for yourself that this is the primary problem and not one of the plethora of other issues that might potentially create difficulties with your car’s air conditioning. Once you’ve determined that your pressure is out of balance and that this is the cause of your air conditioning not functioning properly, you should be able to troubleshoot one of the issues that we discussed earlier that resulted in the pressure imbalance in the first place.
This isn’t the type of work you want to be doing on your own in your driveway, by any stretch of the imagination.