Updated at: 28-03-2022 - By: Lucas

Problems with low-side pressure buildup in air conditioner compressors are prevalent. It’s possible that the business you’re referring to has seen dozens of car owners with this issue already. Even in the sweltering summers, the problem is tough to deal with.

As a result, what causes the low side ac pressure to be excessively high?

The condenser, which is responsible for cooling the air, is the most frequently cited culprit. The condenser has a problem if it moves through its cycles too quickly. This aids in increasing the low-pressure area’s level of stress.

A professional inspection and repair are required if you have determined that this is the problem. This post will explain the issue in further detail so that you may take the necessary action.

Checking The AC Pressure

Ac Low Side Pressure Too High-3

Prior to drawing any conclusions, you should first check the air conditioning pressure. You’ll know for sure if the problem is caused by an excessively high pressure when you perform the pressure check.

To determine the air conditioner’s pressure, you’ll need to purchase a pressure gauge. Costing between $30 and $50, this is a pretty modest piece of hardware. In this price range, a low-cost option is more than adequate for your needs.

The gauge must be connected to the compressor’s low side before the vehicle may be started. Check the pressure in the gauge after you’ve turned the air conditioner up to its highest setting. As a last resort, you can also attach the gauge to the air conditioner’s high side and take the temperature reading there.

Using your vehicle’s service handbook, take the readings and compare them. If your air conditioner is having trouble cooling, you’ll likely notice that the pressure on the lower side is higher than normal.

If you’d want to learn more about this issue, check out this video:

The Function Of The Compressor

A general understanding of how the air conditioning system works may be helpful before you get started. The compressor will be the focus of this section because it is responsible for the majority of the system’s functionality. To be clear, it is responsible for compressing the engine’s coolant.

When the coolant is repeatedly cooled, two pressure sides are created, and these are the ones that exhibit indications of a problem. Compressing the gas is how the compressor raises the pressure.

After that, it’s released and transferred to the condenser to cool down there. As the cycle continues, both sides of the pressure rise.

Pressure Range Of The Air Conditioning System

Ac Low Side Pressure Too High-2

For many automobiles, there are no available service manuals on the internet or in any other place. They have a hard time determining if the pressure is correct. In any case, you need not be concerned because I’ve already specified the average pressure in the compressor.

There are a range of readings from 25 to 230 pounds per square inch on the low side of the gauge. The pressure should be relatively unaffected by changes in ambient temperature.

When the air conditioner is performing properly, you can expect a reading in this range. If the pressure is above this level, you need to get it fixed immediately.

However, despite the fact that this post is focused on the low side, I will only be discussing the high side’s pressure range here.

The measurement falls within the 200-250 lb/in2 range. Even if there is a discrepancy, the low pressure on the high side will not exceed the previously stated range.

The Readings Are Out Of Range

The first thing you need to do is not freak out. This is a rather common problem, but it is one that is easily remedied. If the low-side pressure is at or over 100 and the high-side pressure is 150, then the system is truly out of balance for some reason.

If this is the case, you should avoid using the AC altogether to avoid damaging the compressor. There’s no purpose in using an air conditioner that doesn’t cool since it has a pressure discrepancy.

Why Does The Pressure On The Low Side Go Too High?

Let’s get to the crux of the matter, the reason many of you clicked through to read this article in the first place.

The condenser is most likely to blame if the low side pressure is abnormally high but the high side pressure is normal. In the introduction, I addressed this, but it will be discussed in further detail here.

All the tasks necessary to cool the air and send it to the cabin are performed by the condenser in a cycle. In order to keep the pressure and stability in the system, each process has a set time interval. Compaction cycles can be completed in a flash on some compressors.

As a result, pressure builds up on the low side of the system. When it comes to air conditioning systems, there are many variables to take into account before drawing any conclusions.

It is best to have the inspection performed by a dealership or workshop because they are better equipped to identify the problem.

What Is The Reason For The Pressure On The High Side Being Too Low?

Either the low side is under too much pressure, or the high side is unable to hold it. However, if there is a problem with pressure on both sides, the compressor is most likely to have failed.

The pressure switch may potentially be to blame for the problem. When the pressure on the high side drops too low, it is designed to provide additional power. No increase in pressure will occur if it fails.

Because neither of these problems can be diagnosed at home, you’ll have to pay an inspection fee to be sure.

Why Does The Compressor Have This Issue?

There is a direct link between this section and the one before. It’s not possible for a compressor to reduce its cycle time on its own, is it?

Yes, that is true. The thermostat or temperature gauge is to blame for its irregular behavior. The thermostat regulates and maintains the temperature, while the gauge gathers and records it..

They can malfunction if they are malfunctioning, causing the compressor to malfunction. In fact, the compressor is not always at blame.

There are a lot of moving parts in the air-conditioning system. A single problem can lead to a slew of other problems. If you or the technicians are unsure of the cause of the problem, a proper diagnostic is the only option.

Reasons For High Pressure When The Engine Is Switched Off

Even when the engine isn’t running, a higher-than-normal pressure reading on the compressor’s low side could be due to one of two things. This section of the article should be read in its entirety because both of them are serious.

1. Problems With The Condenser Fan

To keep an air conditioner running, the condenser fan must be working properly. To avoid overheating, it has been designed to cool down the entire system.

Because of this, either the condenser fan is obstructed by debris or it has been damaged in some way. Both of these situations necessitate rapid care due to the possibility of permanent damage to the complete air conditioning system if not addressed.

Aluminum can deform or warp if the condenser fan is under too much pressure. The evaporating coil may leak as a result of this. As a result, this problem must be addressed immediately.

If the AC isn’t working properly, it’s best not to use it until the necessary repairs have been completed.

2. System Is Overcharged

There is no electrical problem if the term “overcharged” is used in this situation. Overfilling the engine with oil or coolant is what this term alludes to. Adding more fluid than the manufacturer recommends will result in an engine that is under too much pressure.

You need to see a mechanic as soon as possible to relieve the stress. The coolant system can potentially be contaminated by air, but this is unlikely.

3. Failing Expansion Valve

A malfunctioning expansion valve may also be to blame. In the air conditioning system, the valve is located near the evaporator and its primary function is to regulate coolant flow through the system.

Depending on the amount of coolant in the system, it can be quite vulnerable to damage. It could freeze or overheat, which could result in serious injury or even death. If the valve fails, the pressure will be unequal.

Things To Check Before Repair

Before shelling out money for repairs, make sure you look into a few things. You may be the victim of a scam if a mechanic charges you a repair cost without first diagnosing the problem. You should take your car to another shop to get looked out.

Pressure switch, expansion valve and compressor clutch should all be checked thoroughly once you’ve found the correct individual. To make things easier, the switch and expansion valve are situated near each other.

An ohmmeter can be used to test the switch’s operation.. This may be the cause of the excessive pressure on the low side if it is giving incorrect readings. If they’re all good, your only option is to replace the compressor as a whole.

Also, I should tell you that the cost of repairs will be high. If you don’t have it done, you’ll be stuck driving about without air conditioning.

Repair Options

Finally figuring out what’s wrong with your air conditioner, you’re ready to have it fixed. In this case, you have a number of options to choose from.

Let’s take a look at each one, so you can decide which one to pursue:

The sooner you get the car to a repair, the better, if you don’t know for sure what’s wrong with the condenser. Make sure to turn off the AC, or you could end yourself needing a new air conditioning unit.

Before you inquire, issues such as uneven pressure in the system, gassing the system will not help in any way. The pressure on the lower side may possibly rise more, resulting in additional problems.

Because you can’t remedy this problem with common household items, YouTube isn’t much assistance here either. If you’re trying to figure out what’s wrong, it’ll come in handy.

It’s quite unlikely that any videos claiming to address a problem with simple tools actually exist. This procedure has a high degree of risk, therefore you should avoid it at all costs.

1. Condenser Fan

The air conditioning system’s condenser fan is essential to its efficient operation. Because it can operate at a variety of speeds, it can adjust to the demands placed on it. In order for the fan to operate at full capacity, the air conditioner must be set to its highest possible setting. You’ve probably gotten the gist of it by now.

What happens if the fan is unable to function properly? First and foremost, the cooling system will overheat.

The only thing keeping it cool is the fan. Because it’s overheated, the air conditioner will also blow chilly air, putting you at risk of irreversible harm.

As a result, how can someone determine whether or not the fan is performing as intended? Use an obd2 scanner to find out what’s wrong with your car.

The OBDII port is plugged into the scanner, which scans the engine for any problems. It will be obvious if there is a problem with the fan.

In situations like this, it is best to replace the fan. If you don’t have a lot of money, you can get a newer one that will run faster and cool the system more quickly.

2. Coolant Discharge

It isn’t that difficult to fix a problem if it is caused by an excess of coolant in the system. Some of the coolants in your air conditioner can be discharged by performing the following actions:

Turn the temperature down.

Assemble a link between the compressor’s suction side and its low-pressure side.

Using a wrench or a hex key, completely close the service valve.

Despite being closed, the high-pressure valve should be left slightly ajar.

Use a jumper to turn on the compressor instead of starting the car.

The low-pressure side should be totally depressurized after the process is finished.

Open all the valves and disconnect everything.

The tools you need may already be in your garage if you are a car aficionado. Mechanics are the people to see if your car is in working order. If one process is performed incorrectly, the system as a whole may suffer.

3. Repairing The Evaporator Coils

If the evaporator coils are causing the problem, it may be because they have cracked.. Cracking a part like this is entirely doable.

When a crack occurs, a leak occurs, causing the pressure to fluctuate. An icing problem may also lead to a blockage in the cooling system, causing the pressure to rise just on one side.

The coils may be restored if the damage isn’t too severe. If they’re beyond repair, you’ll have no choice except to get new ones.

4. Checking The Pressure Switch

Checking the pressure switch in the air conditioning unit may be your last resort if all other choices have been exhausted. As previously mentioned, this switch was built to turn on power if the high-side pressure is too low or vice versa.

If it malfunctions and is unable to do its duty, there will be an issue with the compressor’s pressure regulation. The switch may need to be changed if this happens.


It is my hope that this post has answered your query on what causes the low side ac pressure to rise. The moment it is recognized, immediate action must be taken to address this grave problem.

The compressor may have to be changed as a last resort if the pressure is extremely low and all other options have been exhausted.

Turning on the air conditioning while reading can be uncomfortable, so if you’re one of those people, I recommend turning it off.

I hope you found some value in this lengthy piece, and I wish you luck with the repair!