How To Check Ac Pressure In Car

How To Measure Running System Pressures

Checking Automotive A/C Pressures (do not open valves when checking pressure)

Start the engine and operate the AC system. Perform a visual check to see if the compressor is running.

Was a click heard when the AC was engaged? Is the center hub turning?

Observe the pressure gauges. Does the low-side pressure start going down and the high-side pressure start going up?

After the system runs for a while, raise the RPMs up to about 1,500.

The system should be about 25 to 30 psi on the low side and 200 to 250 psi on the high side. If the ambient temperature is higher or lower than normal the pressures will go up or down accordingly.

Detach The Connector Cable From Clutch Oil

The other method of diagnosis involves detaching the connector cable from the clutch oil. In this approach, keep the disconnected connector safely away from all the other components.

At this point, you now want to use a voltmeter to measure the ground and voltage of the battery. If you cannot find a reading, check the fuse. If you find that the fuse is okay, check the clutch relay.

What Is A Car’s Ac Compressor

The compressor is the part of your air conditioning system that actually creates the pressure that the coolant is under in your vehicle. Obviously, this would be a clear place to look if there’s a pressure issue in your AC system. The reason you have a high pressure side and a low pressure side at all is because the compressor increases the pressure and as it runs through your AC system to the condenser where it changes from a gas to a liquid and it will eventually lose pressure again as the cooling process takes place. Once it circulates back to the compressor it is repressurized as the whole process continues.

If your compressor it’s not working the way, it’s supposed to then obviously the pressure in your AC system can be severely compromised as a result. A new compressor may cost you a couple hundred dollars to buy and get repaired.

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Unusual Car Ac Sounds

When your cars air conditioning system makes unusual noises, this often indicates an AC compressor problem. Unlike refrigerant leaks, this is a sign of a mechanical shift somewhere in your cars air conditioner. One of the most active parts within your vehicle AC system is the compressormaking it a likely culprit.

We All Know How Hot The Texan Heat Can Be

The Texan heat is tough on air conditioning systems, and during the summer months, the last thing you want is to head out for a long drive only to realize your vehicleâs air conditioning is not working. The chemical used to provide cool air is called Freon. Without it, thereâs no way to circulate cold air throughout your vehicle cabin.

Fried Egg Cooked on Texas Car Hood

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How To Test Car Ac Compressor Step : Check No Ground On The Relay Coil

Your PCM may not be generating ground the compressor relay coil if:

The refrigerant is low, or,

The systems pressure is at its maximum level due to the condenser being blocked or the orifice and TMX valve being faulty.

Your job is to find both of them. Which means, the minimum and maximum pressure switch. After that, join the positive probe and the negative probe leads to the correct terminals.

After that, start your vehicles engine and turn on the air conditioning to its maximum setting, and you inspect the multimeters displayed voltage. If there is a voltage on one of the terminals, the PCM is producing energy. Proceed to perform the same test on switch five. If there is power on every switch, you must perform a continuity test on all the switches.

Problems With Ac Pressure

High pressure inside the condenser fan can causes the aluminium to distort and evaporator coils to leak. The cost of repair and replacement of compressor is high as the dash might need to be removed for repair. Higher than normal air pressure is usually a consequence of two situations.

One, your AC system might be facing limited or no airflow through the condenser. This, in turn, might be a consequence of bad condenser fan motor. If you have debris near the fan blocking the flow, you will face the same issue. Second, the other reason for a high-pressure reading can be an overcharged system.

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Ac Completely Stops Working

Unlike the previous one, here, your AC may completely stop working. Well, when it works, sometimes its hard to determine the problem if you are not aware. But in this case, the problem is pretty evident as you will have no air conditioning in your car.

Now, something to consider here is that this problem can occur for various reasons. So, when you see this sign, it doesnt always mean that the AC pressure switch has issues. Several other components are responsible for running your AC.

For determining the exact cause, you can run a test on the switch. I will be discussing that later on in the article.

Low Side Pressure And High Side Pressure

Car AC Not Cooling – How To Easily Check AC Pressure Switch

Before looking at the AC Pressure Chart of R134a Refrigerant, we will try to understand why measuring and monitoring pressure is important in a cars air conditioning system.

In an automotive AC System, a pressurized refrigerant continuously changes from liquid to gas and gas to liquid in a closed loop. The pressure of the refrigerant directly correlates with the temperature.

Based on the pressure of the refrigerant at any particular point in the loop, the whole system can be divided into High-Pressure Side and Low-Pressure Side.

The compressor receives the low-pressure gas from the evaporator. Compressor compresses this low-pressure refrigerant gas to high pressure gas . As this is the starting point of the high-pressure refrigerant gas, the High-Pressure measuring point is located after the compressor.

This high-pressure gas is then transferred to the condenser. The radiator fan near the condenser blows cool air onto the condenser and as a result, the high-pressure gas is converted into high pressure liquid, when it leaves the condenser. Also, the refrigerant releases heat here which it absorbed at the evaporator.

This low-pressure gas absorbs the heat from the cabin and is then sent to the compressor and the cycle starts again. As this is the exit point of the low-pressure refrigerant gas, the Low-Pressure measuring point is located after the evaporator.

NOTE:

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How To Diagnose Car Ac Compressor Failure

How to Diagnose Car AC Compressor Failure

Air conditioning is something many people take for granted until it stops working. It can be annoying if during a hot day, you reach down to crank up your AC and all that comes out is hot air. More importantly a bad compressor can be dangerous. If your compressors bearing goes bad, your engine can seize due to the stuck compressor. If you are traveling at speed and the car shuts off, you no longer have power steering nor is your brake booster functioning. There are a few reasons your AC system might stop working and the central part of it is the AC Compressor. Here are a few ways to diagnose a car AC compressor failure.

Step 1:

If the air temperature does not cool when the AC system has engaged there is a good chance that there was an AC compressor failure. If the AC still works, check to see if the temperature fluctuates while the AC system is running.

Step 2:

Find you AC compressor and visually inspect it for rust, physical damage, oil leaks or paint damage. All of these are signs of a car AC compressor failure. With a lack of oil, the compressor will not function efficiently and will cause premature wear. The increased friction will also lead to erratic temperatures when the AC system is engaged.

Step 3:

Check your belts to ensure there is proper tension and the belts are not damaged. Cracked or splitting belts can cause further damage to your AC compressor. If they are bad, they should be replaced with a new compressor.

The Clutch Engages But The Air Is Not Cold

Step 1: Turn the engine off and install the gauge set.

Step 2: Restart the engine and turn on the air conditioning.

Step 3: Observe the pressure readings.

Though every air conditioning system will vary, you want to see the high side pressure around 20 psi and the low side around 40 psi.
If both the high and the low side are below these readings then you may need to add refrigerant.
If the readings are very high then you may have a problem with air trapped in the system or an airflow problem with the condenser.

If the pressures do not change at all when the compressor engages then the compressor has failed or there is a problem with the metering device.

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Is My Compressor Broken

Diagnose car AC with gauges Ricks Free Auto Repair Advice Ricks Free ...

There can be several reason your compressor may not work, but if youâve checked the electrical system, for any leaks, and the clutch, then it may be that your compressor has an internal mechanical or electrical problem that needs to be fixed.

My recommendation is to replace the entire unit if the compressor is bad. The reason for this is youâll likely save time and money by replacing the old one with a new one. Fairly frequently a rebuilt AC compressor will go bad again, sometimes not too much later after it is reconditioned.

The labor is intensive when taking one out and putting in a new one. If you have to do that twice you end up losing quite a bit of money. And a new compressor really doesnât cost too much more money then getting an old one repaired.

So getting a new compressor will be your best bet in the long run and sometime short term as well. Watch this video if your interested in installing your own compressor. Hereâs another video with more information to help you along the way.

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Its All About The Pressure

Air conditioning systems leverage high-and-low pressure. Before the Freon is converted into a liquid in the high side, it starts out as a gas in the low pressure side of the system. The vehicle is kept cool by the constant circulation of refrigerant through the high and low pressure sides of the system.

Vehicle Air Conditioning System

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How To Test The Compressors Clutches

Step 1

Just open the hood of your vehicle, and find the air compressor. This is located on the upper left-hand side of the engine compartment.

Step 2

Now turn the air conditioner selector knob in your vehicle to an off position, and then start your engine.

Step 3

Now connect the voltage tester to the negative connection on your vehicles battery.

Step 4

Find the wires coming off of the ac compressor, and unplug them. Note that all of the wires should be connected with one wire feed. Then you can place the voltage tester on each of the three connections individually. Note that no activity should be noted on the voltage meter.

Now turn the air-conditioner selector knob to the on position. Then place the voltage tester on each of the three connections. Right now the middle connection should produce activity on the voltage tester, indicating the connection is hot. But if no activity is noted, then your air compressor clutch and wire should be replaced.

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Where Is The Ac Pressure Switch

You can find your AC pressure switches on the units high and low sides. These switches, which have separate switches for the high side and the low side of the system, continuously check and monitor the refrigerant pressure on both sides of the system in an effort to keep the compressor from being harmed by pressure problems.

Key Indicators Of Compressor Failure

Checking Pressures & Charging Automotive Air Conditioning 134A A/C

We mentioned above some typical symptoms of compressor failure, but what do they mean and how do they happen?

Leaks often mean that refrigerant will be escaping the system somewhere along the line. Compressor leaks typically happen around the shaft seal, hoses, O-rings and gaskets. They can be hard to spot and might require the use of a special UV dye or electronic leak detector to locate. The refrigerant also carries an oil mist that circulates to keep everything lubricated. Without enough refrigerant, the aircon cycle will not happen and can result in damage to other parts, not just the compressor.

Odd noises there could be a few reasons for this one. Either internal parts of the compressor have failed which can result in some unpleasant sounds, or something has seized. The compressor clutch or belt pulley is likely here.

No cool air likely due to lack of refrigerant or a failing component, the compressor cant circulate enough refrigerant to keep the system running smoothly.

ECU error if you get a check engine light on your dash, this is a definite sign something more sinister is lurking. The ECU measures voltage signals to parts like the compressor, and can detect malfunctioning signals which might result in incorrect voltage delivery.

Some common causes of failure are:

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How To Lower The Pressure In Car Ac

There are several ways to lower the pressure in your car AC. You can either solve the issues I talked about above or try out a different method. First, lets check out the solutions to the above problems.

When you have a malfunctioning condenser fan, there are two ways to go about it. You can fix the fan, which can be very tough and sometimes impossible. Or you can replace the fan, which is much easier to do. All you have to do is get a replacement fan and replace it. It doesnt take too much effort to fix condenser fan problems.

There are some things you have to do for the contamination issue or leakage issue step by step. The first thing to do is get rid of any contamination through vacuuming. You have to vacuum your system, so it doesnt get contaminated further. Then, clean up the contaminants and seal the leakages.

Keep in mind that this is a fix that isnt permanent. In such cases, its better if you can replace the affected parts.

These are the quick fixes you can try out and see if the pressure in your car AC goes lower or not. If it doesnt, then you can follow the method I am going to discuss now. This method works when you are dealing with an overcharged system. Heres what you will be doing.

First of all, you will need to get the hose you use to fill in the refrigerant. You have to use this to take out pressure from the coolant.

Related: air conditioner problems

How To Diagnose A Bad Car Or Truck Air Conditioner Pressure Control Switch

If the AC pressures are abnormal: Abnormally high or low pressure in the system can both damage the compressor or cause a refrigerant leak that then damages the compressor as the pressure switch has the job of monitoring pressure and shutting down the compressor if pressures are out of range, a check with a gauge set to compare the car AC high pressure side and low pressure side against the manufacturers’ specifications would be diagnostic. The exactly correct refrigerant pressure in a car’s high side and low side depend on the specific refrigerant gas and the specific ambient temperature. . The AC repair manual for the specific AC system or car as well as AC specs for the specific refrigerant will give a table of these pressures and temperatures. Example: for a modern car with current refrigerant, if the outside ambient temperature is 80 degF the low side pressure will be around 56 psi. See details at REFRIGERANT PRESSURE READINGS & CHARTS

If the AC compressor is short cycling that is usually diagnostic of a bad pressure switch

If the car AC compressor does not run at all and if you can spin the compressor motor and clutch with the belt removed I suspect it’s a bad pressure switch. If the motor won’t spin at all then I suspect the motor itself has seized.

Illustration: An Innova OBDL, OBDLL Scan Tool with ABS – used to read the onboard diagnostic codes or OBD codes from the standard connector found on nearly all modern vehicles.

You’ll see one of these codes

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Basic Automotive Air Conditioner Pressure Testing

Mostautomotive refrigerant is today is R134A. Newer vehicles may use R1234YF and this will become more common in the future. Diagnosis of R1234YF systems is different and not covered in this article.Older systems use R12 and while the pressure varies slightly from R134A, the principles are the same. A refrigerant gauge set will have two gauges. The left gauge is marked with blue and used to read the low-side of the system. The gauge on the right is marked with red and reads the high-side of the system. A blue and a red hose are used for attachment to the system. The yellow hose allows a refrigerant to be added and a vacuum to be drawn on the system during service.

Most R134A gauges use quick-connects on the hoses to attach to the appropriate port. These are different from R12 fittings and should not be interchanged. With either system, gauges should only beattached or removed with the engine not running.

When the hoses are attached for the first time, they may be full of air. Purging the lines will remove this air and help keep it out of the system. Connect both hoses to the proper ports and then loosen the other end of the hose at the gauges. The pressure in the system will push any air out of the hose. Quickly tighten the hose and then purge the other line. With quick-connects, the hoses will seal when removed and purging should not be needed again. On systems without an automatic seal, the lines may need to be purged each time they are used.