Abnormal AC pressure gauge readings? (Suits you)

  • Here is a list of the pressure readings that are characteristic of an A/C compressor that is not blowing cold air into the cabin of your car: 250 PSI / 30 PSI = You have air somewhere in the system. 250 PSI / 50 PSI = The system is overcharged and the condenser is not cooling.

What should AC pressure gauges read?

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.

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 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 you know when AC compressor is bad?

Some of the signs of a bad A/C compressor are as follows.

  1. A Lack of Hot Air Being Released Outside.
  2. Loud or Strange Noises From the Unit.
  3. Failure of the Compressor to Turn On.
  4. Circuit Breaker Tripping.
  5. Leaks Around the Air Conditioning Unit.
  6. Warm Air Instead of Cool Air Being Delivered to the House.
  7. Reduced Airflow.

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 are normal auto AC pressures?

These pressures will vary depending on ambient temperature (temperature of the outside atmosphere), but ideally, you will want to see your low side pressure between 30-40 psi and your high side pressure between 150-175 psi.

Why is low AC pressure high?

In this situation, where the high-pressure side of the AC is too low, and the low side pressure is too high, the problem is probably compressor-related. It could also be related to the AC pressure switch, the expansion valve, the evaporator, or the dryer. There could also be a leak in the AC system.

Can a bad AC compressor cause high pressure?

Symptoms for an inefficient compressor are high suction pressures and low discharge (head) pressures. If the compressor is inefficient, the evaporator cannot handle the high heat load due to a decreased refrigerant flow rate and the conditioned space temperature will start to rise.

What causes AC high pressure?

Mechanics often misdiagnose high-pressure gauge readings in a car’s air-conditioning system. Most high-pressure readings are a result of the freon or refrigerant not cooling adequately. Insufficiently cooled freon automatically causes the pressure to increase.

What happens when car AC is overcharged?

Overcharged car ac can lead to some pretty serious repairs down the road if left alone. Additionally this can actually cause your whole ac system to fail as it can also damage the ac condenser. While this is uncommon it does happen. The condenser takes the refrigerant in it’s gas form and pulls the heat away from it.

How do you know if you have a bad expansion valve?

Symptoms of a bad expansion valve

  1. Car AC system isn’t cooling enough or won’t cool at all.
  2. High side pressure is high.
  3. Air coming from vents is frosty.
  4. AC blows cold, then hot.
  5. AC kicks on and then immediately kicks off.
  6. Airflow drops dramatically from vents.

Abnormal AC pressure gauge readings

This is the second installment in a series on the readings from an alternating current pressure gauge. If you missed part I, you can find it here. I’ll go through everything in this section.

See also

Abnormal Auto AC Pressure Gauge readings and what they mean

While your gauges and pressures appear to be OK based on the temperature-pressure chart below, your air conditioning system isn’t cooling as effectively as it should be. 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.

75°F Low side pressure (35-45 psi) is present at the ambient temperature.

  1. 80°F Low side pressure (40-50 psi) in the ambient temperature range Side pressures of 175-210 psi are common.
  2. Side pressures of 225-250 psi are common.
  3. High side pressure (between 250 and 270 psi) 95°F Pressure on the low side of the atmosphere is 50.55 psi.
  4. High side pressure (between 315 and 325 psi) 105°F Low side pressure (50-55 psi) in the ambient temperature range Side pressures of 330-335 psi are common.
  5. High side pressure of 340.345 pounds per square inch

Here are the possibilities

1) The blend air door or actuator is not functioning properly, and you are receiving warm air from the heater core that is mingling with the chilled air from the air conditioning system. Check blend door function by moving the temperature dial on your car’s HVAC system and keeping an eye on the blend door operation as it changes temperature. If your vehicle is equipped with a heater valve, be certain that it is not allowing hot coolant to enter the heater core when the air conditioning is running.

  1. 2) Air and humidity have accumulated in the system as a result of leaks and refills throughout the years.
  2. The refrigerant in the evaporator core becomes extremely cold as a result of this, which causes ice to develop on the fins of the evaporator core.
  3. The evaporator heats up as a result of the lack of refrigerant flowing through it, causing the ice to melt and the air to become heated.
  4. Evacuate the system as a workaround.
  5. Replace the accumulator (orifice tube system) or the receiver/dryer if they are damaged or worn (expansion valve system).

Recharge. In the third instance, the heater core is leaking hot coolant into the heater box. Vents will emit an enticing scent, and there may be greasy deposit on the glass, which you will notice. The amount of coolant in the engine will be low. Replacement of the leaking heater core

AC symptom2: Low side pressure is too low, High side pressure is low

1. If the temperature outside is really low, this may be considered normal. There is no need for a fix. When the temperature rises, double-check your findings. 2) Insufficient refrigerant charge (most common cause). Check for leaks and make the necessary repairs. Remove the refrigerant from the system and recharge it with the proper quantity of refrigerant. Partially blocked orifice tube/expansion valve as well as the evaporator are possible causes. Because of a blockage or a jammed expansion valve, the passage of refrigerant into and out of the evaporator is restricted.

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Replace the orifice tube and cleanse hoses if they are blocked.

Replace the expansion valve and cleanse the system before installing the in-line filter.

Evacuate the area and look for a clog.

AC symptom3: Low side pressure is too high, High side pressure is high

1. If the temperature outside is quite high, this may be considered normal. 2. There is an overcharge on the system. If you’ve attempted to add refrigerant manually, this is a relatively regular occurrence. Remove any surplus refrigerant or empty the system and re-charge it with the proper quantity. 3. The condenser fins are blocked, and the condenser fan is not operating or is not operating at the proper speed (most common cause). When it comes to eliminating heat from freshly compressed refrigerant vapor and permitting it to condense into a lower pressure liquid, airflow over the condenser is crucial.

  • Cleaning the condenser fins and checking for damaged condenser tubes are the recommended solutions.
  • 4.
  • Replacement of the regulator valve is the solution.
  • A blockage on the high-pressure side of the system, which occurs between the compressor and the condenser, but before the high-pressure port Evacuate the area and look for a clog.

AC symptom4: Low side pressure is too high, High side pressure is low or normal

1. The expansion valve has become jammed open, 2020. Rick Muscoplat is a professional musician. Rick Muscoplat posted a blog entry on

AC Manifold Gauge Readings

A manifold gauge set is used to measure the pressures of refrigerant within an air conditioning system. The high and low sides of a car air conditioner are separated by a metering device and the air conditioning compressor. When the clutch is engaged, a compressor draws low-pressure vapor in from the suction side of the system through the intake. It compresses the gas and discharges it at a greater temperature and pressure via the discharge side of the compressor. These pressures and temperatures are extremely predictable, and they are influenced by the ambient or outside air temperature conditions.

It is possible that the compressor is not operating correctly when the low side is high and the high side is low.

Pressures are equalized and very near to each other when a system is static, meaning that it is not in action at the time.

Occasionally, a faint hissing sound can be heard while the pressures are equalizing and soon after the system has been shut down. As the compressor wears down and becomes weaker, the high and low side measurements of the system begin to approach static values more frequently.

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.

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Refrigeration Compression Ratio

For the chemist to generate reactions, he or she needs heat, pressure, and reactive substances at their disposal. He or she use equipment to look for improved approaches to ensure that a reaction proceeds more quickly and comprehensively. The chemist is frequently required to provide large amounts of heat in order to complete the reaction. The individual who provides refrigeration servicing and installation has a powerful chemical reactor at his or her disposal. He or she possesses a plethora of reactive materials, such as refrigerant, oil, cellulose, copper, oxygen, moisture, acid, and so on.

  • The last thing we want is for a refrigeration system to cause chemical reactions in the environment.
  • The qualified service expert can do a great deal to reduce the severity of these reactions.
  • A disproportionate number of systems are built to ‘meet a competitive environment.’ It is one thing to design a work in such a way that it is as cost-effective as feasible while yet being proper.
  • According to studies, fewer than 10% of service personnel are aware of how to compute compression ratios, let alone what the ratio represents.
  • The rate of chemical reaction increases by a factor of two for every 18°F increase in discharge temperature!
  • The compression ratio has the greatest impact on discharge temperature of any other factor.
  • Pressures in absolute terms Due to the fact that a refrigeration system is a closed system that is not exposed to atmospheric pressure, we must deal in absolute pressures rather than gauge pressure readings when determining a refrigeration system’s compression ratio.
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It is simple to acquire absolute pressures, P.S.I.A., at zero or above gauge readings, P.S.I.G., when the gauge readings are zero or above.

to the gauge reading to get the desired result.

are straightforward to determine as a result of this.

suction pressure that is causing the greatest confusion.

We can now calculate the following equation to determine the compression ratio: Example: As seen on a conventional manifold gauge set, a system is operating at a head pressure of 160 pound per square inch.

Changing from P.S.I.A.

: PSIA Head Pressure = 160 + 15 = 175 Lbs.


Suction Pressure=30 – 10=20=10 1 Compression Ratio=175=17.5: 1 10 This particular sample system is in serious peril!

The high compression ratio will result in high discharge temperatures, which will result in a large number of burnouts.

Head pressure = 160 plus 15 equals 175 psi Suction Pressure = 10 + 15 = 2525 P.S.I.A.

Suction Pressure = 175= 7:1 P.S.I.A.

This system is expected to survive for a long period.

The compression ratio is not affected as much by changes in head pressure as they are by changes in suction pressure.

would be the head pressure in both of our cases.

High compression ratios are a key contributor to the overheating of systems.

There are a variety of additional reasons why a system may have high discharge temperatures, but understanding how to calculate the compression ratio may tremendously assist a service professional in determining what is wrong with a problematic system.

AC low port pressure too high

Personally, I’ve converted my Porsche 940 to run on R134a gas. I also replaced every component during the procedure, including the under-dash evaporator, because I was on the lookout for a leaking component. When it came to individual automobiles, I felt it was inappropriate to refer to specific documents. After replacing my condenser and evaporator, I’m making the educated guess that my overall volume has altered from the original specification. Remember to let your automobile rest until it is completely cold and in balance with the ambient temperature before determining the suitable charging procedure (park it in your garage, roll down the windows).

  • This will provide you with a very accurate idea of the charge remaining in the system.
  • Find your ambient temperature and the point at which the line crosses the pressure line; this is what you should be seeing on your low side pressure gauge.
  • To measure the ambient temperature, place a thermometer immediately next to the condenser.
  • The first spike that occurs when you open the can of r134a is totally OK; however, an excessively high pressure that persists for an extended period of time is not acceptable.
  • In addition, be certain that your manifold gauges are fully open.
  • If you want to obtain the best approximation of what your low side pressure should be when monitoring it while charging, always reference the local ambient temperature and humidity with gauges while measuring the low side pressure while charging.

Why Is AC Pressure Too High? Causes And Solution

Everyone wants a cool automobile in the summer, especially if they’re going on a lengthy trip. The air conditioning appears to be malfunctioning at times, and the air temperature is just slightly cooler than normal. I’m wondering if my engine is running too hot or if there’s something else wrong. The operation of the air conditioning (AC) system is critical since it is responsible for keeping the interior temperature of the vehicle under control. If the pressure in your air conditioner is consistently too high, it may indicate an underlying problem.

When I put on the air conditioning and it’s still warm, I’ll occasionally turn up the fan in the hopes of getting things colder more quickly.

We’ll talk about how the pressure in your air conditioning system might indicate the overall health of your system. What Causes Excessive AC Pressure? The Reasons for the Problem and the Solution

Importance of the AC Readings

Higher than typical temperature readings while testing your air conditioner might indicate the presence of other problems. High temperature readings from your air conditioner may indicate that harm is being done to your air conditioning system. It must function within a specified pressure range in order to be effective. The presence of excessive pressure may eventually result in the failure of the compressor. If the problem is not repaired in a timely manner, the repairs might be quite expensive.

Problems with AC Pressure

The high pressure within the condenser fancan leads the aluminum to deform and the evaporator coils to leak, resulting in a faulty cooling system. Because the compressor may need to be repaired or replaced, the cost of repair and replacement is considerable (about $450 + $700 labor – price varies widely depending on automobile) because the dash may need to be removed. Air pressure that is higher than normal is generally the result of two circumstances. One possibility is that your air conditioning system is experiencing restricted or non-existent airflow through the condenser.

If there is debris near the fan that is obstructing the flow, you will experience the same problem.

Condenser Fan Problems

Photo credit: The condenser fan of an air conditioning system operates at a variety of speeds and capacities. As a result, a failure may result in a reduction in both efficiency and speed. This, in turn, results in the fan’s inability to efficiently cool the system and circulate air. With readily accessible DIY equipment, you may choose the fan’s speed on your own personal time.

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Problems with the AC System

Most of the time, overcharging of the system is caused by an excess of refrigerant present in the system. It is also possible that there is too much oil in the system. In order to check for an overcharge system, you would need to monitor the pressure within the system itself. Make it a point not to add extra refrigerant to the air conditioning system until you are certain that it is low. Check for leaks first to prevent the system from becoming overcharged. Purchase a leak check kit or a gas sniffer (Amazon Link) to determine whether there is an underlying leak.

  1. Keep an eye out for leaks in the pipes, hoses, and compressor when conducting your inspection.
  2. If you do a visual check and see oil pouring from any of these spots, you will have determined that there is a leak.
  3. R12 is commonly seen on older model automobiles from the 1990s and before.
  4. Overcharging the system and leaks are two of the most typical causes of air conditioning problems.

It is necessary to evaluate both the AC low and high pressure side readings in order to make a particular diagnosis. Use a pressure gauge to check it out for yourself (Amazon Link)

  • After monitoring pressure using gauges, if both the high and low pressure side readings are greater than 150 psi when the engine is turned off, you may have overcharged your system and should consult a professional. It is possible that you may need to remove pressure from the system. Check your car’s owner’s handbook for the proper tire pressure. Because low or zero pressure indicates that there is little to no refrigerant in the system, you should examine for probable leaks. Inspect the AC pressure lines after starting your car and turning the air conditioning up to maximum setting. The low pressure side should read approximately 30 psi, and the high pressure side should read around 250 psi. Specific recommendations can be found in your car’s owner’s handbook. The pressure will cycle between the low and high sides, therefore you must wait until the clutch engages in order to obtain accurate measurements. If there is pressure on both sides of the vehicle but the readings are incorrect, it is probable that a component in the air conditioning system is malfunctioning. When readings are incorrect, the compressor, clutch, and expansion valve are frequently the source of the problem. If you need to add refrigerant because the pressure is low while the engine is turned off, see your mechanic. First, check to see that all of the other components of the air conditioning system are functioning properly. Then you’ll need to acquire some refrigerant and fill it up to the proper specs specified in your automobile handbook. (Amazon Affiliate Link) It’s a good idea to see a professional if you need to remove pressure from your air conditioning system. There are legal (Environmental Protection Agency) and safety problems if you attempt to do it yourself
  • Nevertheless, there are other difficulties that can be resolved by yourself if you have access to additional instruments. Decide how much effort you are willing to put in and shop around.

System Blockage and Restrictions

If there is a clog or restriction in the air movement through your condenser, the high pressure side measurements will be elevated while the low pressure side readings will decrease with time. In order to resolve this issue, you must first remove any obstructions and debris from the area. Check the readings once again once the debris has been removed. Unless the problem is resolved, it is quite probable that something within your system requires repair. Image courtesy of: It is quite rare to see high low side pressure measurements in conjunction with typical high side pressure values.

The cycles are cutting in and out too quickly, resulting in those extreme low side values.

The high low side readings (along with typical high side readings) are the consequence of a malfunctioning thermostat switch.

You would need to have the thermostat switch changed by a local repair in order to get normal readings again.

Excess refrigerant should not be added to the system.

Performing a comprehensive assessment of your air conditioning system prior to making any repairs is, in my opinion, the best approach.

Consider taking your time at the start and making sure you grasp everything before you make a costly error, in my view.


If your air conditioning system is not functioning correctly, it is time to get it inspected. With the help of a pressure gauge that displays the high and low pressure line readings, you can identify a variety of issues on your own. Additionally, you may perform a visual examination, use a leak detection kit, or use an electronic sniffer to check for leaks on your own. When it comes to larger repairs and relieving pressure from your air conditioning system, I recommend that you consult with a professional mechanic for the best results.

Additional Questions

So, what should I do if the condenser fan isn’t working correctly? While the engine is running, put the air conditioning up to the maximum setting and open the hood. In order to determine whether or not the condenser/radiator fan is activated, wait 5 minutes or until the automobile achieves normal operating temperature. Turn off the car and wait 30 minutes for everything to cool down if the fan isn’t turning on automatically. Check to see if anything is interfering with the fan’s ability to turn.

Electrical connections should be checked. If everything appears to be in working order, it is possible that you may need to replace the fan, the temperaturesensor, or something involving circuitry, such as the fuse for the condenser fan.

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