Almost every driver has found himself in a situation where he is feeling too hot in the car. The sun is up, the temperature is rising, and the AC is cranked up, but nothing is happening. The common reason for this is when a low-side AC pressure gets too high.
But what is causing it? The first thing to look out for is the compressor. It is a vulnerable part of the AC system and can cause many problems. Also, the problem can be in the expansion valve, on the AC pressure switch, or the dryer.
Most of these terms don’t mean much to many of us. Stay with us, and you will learn all about this common AC problem and how to fix it.
What Is the Low Side of an AC System in a Car?
The low side is usually found between a compressor and the evaporator. You can start by finding the compressor. You can find it near the radiator right in front of the vehicle. A compressor is driven by a belt which can help you identify it.
When you find it, you can proceed to find the evaporator. Those components are connected by a line that you can follow. The evaporator is located directly under the windshield, behind the dash. The service port of the low side is located on the line that connects the evaporator and the compressor.
What Is the High Side of an AC System in a Car?
The high side of an AC system is connecting the compressor with a condenser and then goes through the dryer. When it goes through the dryer on the line you can locate a high-side service port.
The AC flow starts in the compressor. When the refrigerant goes into the compressor, it is in the form of gas. In the compressor, the gas is compressed and, with the help of the pump, is forced out to the condenser. There the now-heated gas is cooled down. During the process, some amount of gas is turned into a liquid.
This cooled-down liquid is then moved to the dryer on the high-pressure side. The dryer will absorb moisture. This, now a high-pressure liquid, will flow to the thermal expansion valve. There it will be converted into a low-pressure liquid, finishing its cycle in the evaporator.
Low Side AC Pressure High: Why Is It on
If your AC is fanning in the cool air in the cabin space, there are several potential causes to look out for. The most common are
- Blocked or restricted airflow
- Leaks in the refrigerant system
- Failed compressor
- Overcharged AC
Blocked or restricted airflow
If the air cannot flow through the system or it is restricted by the blockade, that can cause high pressure in the air conditioning system.
If the blockage restricts the work of the condenser fan, that will cause a problem with the pressure. Identify the blockage and remove it. Check the pressure readings again, and if the problem remains, then the problem can be in some other part of the system.
A dirty evaporator is often the problem that restricts the low airflow. If the air cannot freely flow through the evaporator, the air conditioning will not function. Dirt, leaves, or plastic bags can block the evaporator. This minor problem can be solved easily by cleaning the evaporator.
If you think airflow is blocked, check for air filters. Dirty air filters will block the flow of cool and hot air.
Pro Tip: Filters must be changed regularly because they easily get dirty.
Leaks in the refrigerant system
Leaks from the evaporator coils are the most common causes of leaks in the air conditioning system. The pressure can also rise because of the ice buildup caused by the coil problem. The ice blocks the airflow resulting in the rise of the pressure.
Refrigerant leaks can happen anywhere in the system. But the most common spots for leaks are the evaporator, condenser, and compressor.
Vehicle Failed compressor
If the compressor is not working, refrigerant cannot circulate through the AC system. Without refrigerant circulation, you can’t get any air conditioning in the cabin. The common reason for this malfunction is if you don’t use the AC for a prolonged period.
From this, you can learn that you must occasionally turn on the air conditioning system. That way, you are keeping the ac compressor functional and working.
If you are using your AC regularly and still think that the problem is in the compressor, check this list of common symptoms:
- Leaks
- Strange noises when starting AC
- No cool air is coming from the car’s AC system
Overcharged AC
One of the common mistakes when refilling the AC is adding excess refrigerant. You will notice a high pressure in the AC even when you turn off the engine. The issue with an overcharged AC system needs to be resolved. An overcharged system will not fix itself. The best way is to go to the mechanic because refrigerant is highly toxic.
High AC Pressure: Top Causes In a Car
When diagnosing high AC pressure, the problem is usually in the low refrigerant level, faulty compressor, or thermostat.
High Ambient Temperatures
When the hot days of summer and spring arrive, the constant need for cold air from the AC comes in. If you notice the temperature in the cabin is high even with the AC running, then you have a problem. High overall temperatures can show problems with the low side AC pressure.
The first thing you should look out for is the compressor. Usually, the culprit is the malfunctioning clutch. If the compressor is okay, the second thing to look at are refrigerant levels. A leak in the system will cause the refrigerant level to drop. With no refrigerant, AC pressure will drop, and there will be no cold air in the cabin.
Low Refrigerant Charge
Leaks in the AC system are common. If you notice that you need to refill the refrigerant every year, then your AC system is leaking. The mechanic should check the whole system and find the leaks. If the AC works with low refrigerant levels, it can be damaged.
A low refrigerant level will also cause low-side AC pressure to be high, which is also bad for the whole system. Refill your AC if needed, and try to find and seal the leaks.
Failed or Malfunctioning Thermostat
A thermostat is a device that measures the temperature. The air conditioning system works as a control device. It is constantly measuring and controlling the temperature. When required, it will regulate the flow of the refrigerant in the radiator. The thermostat will block or allow the refrigerant to the radiator, thus controlling the temperature.
Keeping the thermostat working properly is very important for the whole air conditioning system. Coolant needs to be checked and replaced regularly. Also, a visual inspection of the thermostat can prevent major malfunction in this component.
The thermostat should be inspected if you notice strange jumps in the temperature readings. It can also lead to low pressure in the AC system.
Another symptom of a faulty thermostat is increased fuel consumption. If the engine cannot reach its working temperature, it will consume more fuel. Usually, the thermostat is changed with the water pump and the timing belt.
Worn or Damaged Compressor Clutch
The AC compressor clutch should be engaged when the AC is working and disengaged when it is not working. But everything has a limited work life, and so does the clutch. It can become damaged or worn during work, causing the whole compressor to work badly.
If you notice that the compressor is struggling with power, then the clutch can be a problem. Be sure to confirm this. If the clutch is the problem, replace it as soon as possible. Leaving this problem unresolved will lead to bigger problems in the future.
How to Vacuum AC System in a Car?
For this procedure, you will need specialized equipment to measure AC pressures and vacuum the system. That can be done with the gauge set. It needs to be connected to the low and high-side pressure ports.
- Park the vehicle on the flat terrain and apply the emergency brake. Turn off the engine, and prepare safety gloves and eyewear. The low side of the system should be between the evaporator and the compressor
- Prepare the gauge set. Check the connections and how tight they are. Bad connections can cause a leak. The red gauge and the connector valve are the high-pressure sides of the system. The blue gauge and the second valve are the low-pressure sides of the system. Before you attach the gauges be sure that they are closed. The hose in the middle is connected to the vacuum pump and the new can of refrigerant
- Connect the valves to the system. High and low side valves can be connected only to their ports to avoid confusion
- Connect the middle hose to the vacuum pump. This will remove any moisture and static air from the system
- Slowly open the gauge on the low side. The pump will slowly suction the vacuum out of the system. The noise coming from the pump will change once the pump starts taking out the air from the system. Leave the pump working for 30 minutes, and the system should hold at around 28 to 29 inches. If the system can’t reach those values, then there is a leak in the system
Check Out How To Pull A Vacuum On Your AC System And Recharge Your AC System:
What Causes Low Side Ac Pressure Too high: FAQs
What Happens When the AC Pressure Is Too High?
Problems with high pressure in AC systems are easy to diagnose. When the AC is not working properly, the common problem is the high pressure. The problem can be on the low-pressure side and the high-pressure side. Additional inspection is needed to determine the exact cause.
How do you Check Your AC Pressure?
AC pressure is checked with specialized equipment that has AC pressure gauges. This equipment can measure high-side pressure and low-side pressure with a pressure gauge.
How to repair an Overcharged AC?
The best and safest way is to go to a certified mechanic. The refrigerant is highly toxic, and handling it demands care. The mechanics have a special vacuum and other specialized equipment. They use it to suck all the refrigerant out of the system. Too much refrigerant is dangerous for the system and should be fixed.
What Is the Symptom if the System Is Overcharged With Refrigerant?
If you think that you have a problem with the overcharged AC system, you should look for these symptoms:
– Overall poor cooling. The AC removes the warm air and moves it out of the vehicle. The AC cannot remove the warm air fast enough if the system is overcharged.
– Noisy compressor work. If you can hear your compressor working, then it is in trouble. If it keeps working like this, it can break down completely. It is vital to prevent further damage because a new one can cost over $1000.
– AC pressure is high. Suppose the car’s AC compressor works hard to keep the temperature low. If the system is overcharged, all that hard work will cause high pressure in the system. This state will also damage the compressor
– Problems with the car engine. When the AC is overcharged, it will draw a lot of power from the engine. In the long run, this can damage the engine.
How Many Cans will Need to Recharge My AC?
Most vehicles need between 28 and 32 ounces of refrigerant. Larger trucks and SUVs will demand more. A can hold 12 ounces of refrigerant, so you will need 2 or 3 for your vehicle. Before trying this yourself, check the owner’s manual for more information.
Final Considerations
If you live in an area with long summers with a lot of moisture, driving a car without AC is torture. Having a functional AC has become a necessity for almost everyone. Unfortunately, the AC system can have so many problems that you must regularly control it.
We mentioned all the common and less common problems that can trouble the AC and how you should react. Keep an eye on any symptom that can be a problem for an AC, and don’t wait to go to the mechanic!
