Diagnose Hyundai AC compressor with variable displacement and external control valve? (Solution)

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Diagnose AC problem with Hyundai AC compressor with variable displacement and external control valve 1. Start the engine, set the blower speed to level 2, and select MAX AC with the coldest temp setting.

How do you check a clutchless AC compressor?

Start the car and turn on the ac. Using the clt, raise the input level until you see three or four dots on the clt. This will open the solenoid on the rear of the compressor allowing refrigerant to enter the pump; you will then see some movement on your gauges.

What does a AC compressor control valve do?

The function of the valve is to balance the pressure of the fluids moving through the system by controlling the angle of the swash plate. This keeps the evaporator at a constant temperature slightly above freezing to maximize the auto air conditioning system operation.

What is a variable displacement AC compressor?

A variable displacement compressor eliminates the need for a cycling clutch by altering the compressor’s volume based on system demands. The system’s clutch is left engaged while the system is in use. They are disengaged if there’s a problem or shut down.

What causes AC compressor failure car?

Loss of Lubrication Most Common Reason for Compressor Failure. Loss of lubrication is unquestionably the most common cause of compressor failure. This can happen when there is a refrigerant leak somewhere in the system that allows refrigerant and oil to escape.

What is the reason for swash plate compressor failure in car AC?

Reason: It may be caused by a clogged expansion valve that blocks the refrigerant from flowing into the evaporator. This may also be a cause of a damaged compressor clutch that prevents the compressor to maintain the correct pressure. Or it may also be a sign of a blown fuse or leaks.

What is a clutchless AC compressor?

Clutchless means that the compressor no longer has an electromagnetic clutch. This means that the compressor is permanently driven via the pulley and works even if the air-conditioning system is switched off.

How does a clutchless AC compressor work?

How a clutchless AC compressor works. As the name implies, a clutchless AC compressor doesn’t have a clutch to engage and disengage the compressor shaft from the drive belt pulley. Instead, the drive belt turns the compressor shaft all the time.

What is the difference between automatic compressor and manual compressor?

Technically there is no difference between a compressor used on an automatic vehicle and a manual vehicle.

How do you diagnose a bad compressor valve?

Being able to recognize the symptoms of a faulty valve are essential, and Adeszko said problems can stem from a number of things. “The symptoms could be a loss of cooling or refrigeration, higher-than-normal suction pressures with low discharge pressures, the compressor being very quiet, or low amp draw,” he said.

How do you test a compressor valve?

To check the suction valves in the compressor, turn off the indoor blower motor and turn the unit on.

you should see the suction pressure start to drop and continue to drop.
If the suction pressure does not drop, chances are the suction valves in the compressor are bad.

How do you know when AC compressor is bad?

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

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.

What controls a variable displacement compressor?

SDV is an internal variable displacement compressor of which discharge capacity is controlled by detecting the refrigerant pressure in the air conditioning system with a sensor installed in a compressor.

What change happens to a variable displacement compressor to change its performance?

Unlike the old fixed displacement compressor (FDC), the variable displacement compressor (VDC) automatically varies its pumping capacity to meet air-conditioning demands. When the car’s cabin temperature is high, it increases its refrigeration capacity until the desired temperature is reached.

Diagnose Hyundai AC compressor with variable displacement and external control valve

South Korea’s Hyundai Motor Company has published a service bulletin17-HA-002 to remedy an air conditioning issue in which:The air conditioning does not get cold enough On the manifold gauge, anomalous system pressure is indicated by the high and/or low sides (normal pressure should be130-psi at idle on the high side with AC set to MAX)

Also interesting: Diagnose Hyundai AC compressor with variable displacement and external control valve? (Solution)

Diagnose AC problem with Hyundai AC compressor with variable displacement and external control valve

South Korea’s Hyundai Motor Company has published a service bulletin17-HA-002 to remedy an air conditioning problem in which:The air conditioning does not get cold enough On the manifold gauge, the high and/or low sides indicate anomalous system pressure (normal pressure should be130-psi at idle on the high side with AC set to MAX)

How to check for a sheared torque limiter slip clutch

If everything is working properly, the center bolt located at the front of the pulley will revolve at the same speed as the pulley during normal operation. If the pulley rotates but the center bolt does not, this indicates that the torque limiter slip clutch has broken as a result of internal binding and that the compressor must be rebuilt. If the middle bolt is spinning, move to the next step in the diagnostic process.

Conduct the ECV resistance test

Make use of the diagnosis kit in Hyundai component 00305ACKIT TOOL to connect a multimeter to the leadsExternal control valve from the ECV and verify the resistance between them. The package includes the extension harnesses that are required for testing. Normally, when the ambient temperature is 77°F, the normal ECV resistance should be 10.1 11.1 ohms. The resistance, on the other hand, may vary depending on the temperature beneath the hood. The permissible range is (8 x ECV Resistance x 14 x ECV Resistance) Replacement of the ECV is necessary if the resistance falls outside of the allowable tolerance range.

Conduct the AC pressure test

Making use of the test kit in accordance with the directions. As soon as the engine is running, turn on the blower at speed 2, with the selection set to MAX and the engine running at idle speed. Check the air conditioning pressures by turning the kit switch to the ON position. Low side pressure should be between 20 and 40 psi, while high side pressure should be between 130 and 190 psi. If you execute this test for more than 30 seconds, you may have evaporator core freeze up or expansion valve freeze up, which can be dangerous.

Make any necessary repairs to any broken wiring or connections.

Remove the refrigerant from the system and replace it with the proper charge.

Check the pins of the ECV valve for corrosion, damage, or bentness. If no further issues are discovered, the ECV should be replaced. The year is 2021. Rick Muscoplat is a professional musician. Rick Muscoplat posted a blog entry on

Diagnosing Variable Displacement Compressors

When the compressor’s cycling clutch was engaged in older air conditioning systems, the compressor ran at maximum capacity all the time. If the engine was running and the clutch was engaged, the compressor would be pushing air through the system. And the greater the speed at which the engine turned, the greater the amount of pressure that the compressor created. Disengaging the clutch and allowing the compressor to rest for a period of time were the only methods available for modulating the pressure produced by the compressor.

The most significant drawback of this configuration is that it compels the compressor to operate at maximum capacity at all times, regardless of the ambient temperature or the temperature demands placed on it by the vehicle’s occupants.
The variable displacement air conditioning compressor corrects some of these problems by altering the method in which the air conditioning system functions.
This permits the pressure created by the compressor to be transferred gradually rather than all at once, resulting in less damage to the compressor.
This is especially useful while traveling at highway speeds.
A DVOM would detect the on time as a voltage of between 6 and 7V at this moment, according to the manufacturer.
The greatest and lowest voltage readings would be displayed on the Min/Max record, whereas a scope would display a voltage signal with a pulse width of 50 percent on the scope (on time vs.
There are a number of different variable displacement compressor manufacturers, but the diagnostic method for each is quite similar to the others.

Direct-drive compressors are those that are exclusively controlled by a pulse-width modulated voltage signal.

The second kind is essentially the same as the first, but it includes a typical electromagnetic clutch that is positioned on the compressor shaft as an additional feature.

If the refrigerant seeps out of the system, there is no pressure to force the refrigerant oil through the system, which results in the system failing.

It is possible that a catastrophic compressor failure will occur.

This is why identifying refrigerant leaks on systems using direct-drive compressors has never been more critical to extending the compressor’s life than it is right now.

If there are any leaks around the Schrader valves, I use an inches of water (in.-H 2 O) pressure gauge linked to a flexible hard-plastic hose to check for them.

Even a very slight leak will cause the gauge to increase inexorably and continuously.

The diagnosis of variable displacement compressors is essentially the same as the diagnosis of old-style compressors in most cases.

In order to determine if there is adequate pressure to operate the system, examine the signals sent to the compressor.

Check for varied voltage to the control solenoid on the rear of the compressor after that to see whether it is working properly.

At this stage, the readings on the a/c manifold gauges should indicate that the pressures are normal.

On a scan tool, certain systems will display the compressor voltage/amperage that has been applied.

This will provide an answer to the query.

If the cabin interior temperature falls below a certain threshold, the system may begin to reduce the amount of control signal sent to the compressor.

If you get to that stage, you could suspect you have an issue with refrigerant flow.

Assume that the cabin temperature has now decreased to 45 degrees Fahrenheit.

The pressures on your manifold gauges would be influenced as well.

Adding refrigerant at this time has the potential to cause the system to overcharge.

In order to ensure the safety of the compressor, it is equipped with a plastic shear pin or hard rubber clutch plate (which is comparable to a harmonic balancer) that drives the compressor shaft.

Remove the drive belt tension in order to inspect the clutch.

(See illustration) If the clutch freewheels and/or a portion of it does not turn, it is likely that the pin or the clutch rubber has sheared for some reason, which is not immediately apparent.

A problem with input signals to the a/c module is another sort of issue that might cause the system to fail to function properly.

Typically, if a sensor is completely out of range, a code will be generated.

When has it happened to us that the compressor has failed to switch on because a temperature sensor has reported that the engine is overheating?

Before anything else, make sure the voltage signal at the pulse-width modulated compressor solenoid control wire at the a/c control module is in good working order.

After that, look for codes in the a/c control module.

Some system modules have been configured to turn off the air conditioning system if particular codes are entered into the system.

Starting the car and adjusting the air conditioning settings for optimal cooling while setting the blower speed to High are the next steps.

While keeping an eye on the scope, jab the throttle all the way to the floor.

On some cars, the pulse width on time may be reduced to just 10% of its maximum value.

When the compressor is turned back on, the scope pulse-width modulated signal may only reach 40 percent of its maximum value, then gradually grow to 95 percent of its maximum value over time.

The way in which one manufacturer controls the compressor may differ slightly from the next.

While repairing the system, it would be prudent to keep an eye on the pulse control signals going to the compressor once again. It may increase the cost of the service, but it will assist to reduce the number of repeat customers.

Adjusting a Variable-Displacement Compressor or Converting It to Function as a Fixed-Displacement Compressor

Victor works as a businessman, an engineer, and a professor. He has a strong interest in automobile repair and maintenance. When it comes to air conditioning systems in modern automobiles, a typical complaint is that there is inadequate or no cooling at higher engine speeds—a issue I’ve never had with earlier cars. It is very comfortable in the car’s interior while it is running at idle, and the low-side pressure is 40 psi and the high-side pressure is 200 psi (as measured by a manifold gage).

It’s as though the clutch has been released from the transmission.
We’ve tried a variety of different approaches to solving the problem.
This article will cover the strategies that have been proven to be effective.
My recommendation is that you read my other essay, ‘Variable Displacement Compressor—How It Works,’ first.

The strategies given in this article are applicable to Variable Displacement Compressors that are controlled from the outside. However, although the same idea may apply, externally operated Variable Displacement compressors may necessitate a somewhat different technique. These strategies are only relevant to compressors that have a strong pumping action at the time of application. They will not operate on a faulty or underpowered compressor. We have no choice but to replace a faulty compressor if the first one fails.

Three Solutions to the Problem

The approaches described in this article are applicable to Variable Displacement Compressors that are controlled from the outside. However, although the same idea may apply, externally operated Variable Displacement compressors may necessitate a different procedure. If your compressor still has a decent pumping action, these approaches will only work for you. If the compressor is weak or malfunctioning, they will not function properly. Unfortunately, we have no other option except to replace a failing compressor.

Option 1

If the displacement control valve is adjustable, make the necessary adjustments. It is not possible to modify the displacement control valves in some compressors.

Option 2

If the displacement control valve on the variable-displacement compressor is not adjustable, convert the compressor to operate in fixed-displacement mode. You simply must be prepared to tolerate a minor reduction in performance, notably in terms of smoothness of operation and fuel efficiency, as a result of the modification. A variable displacement compressor operates more smoothly and quietly than a fixed displacement compressor, and automobiles equipped with this type of compressor consume less gasoline than cars equipped with fixed displacement compressors.

When our drivers switch on and off their vehicles after the conversion, the only difference they have noticed is a little clicking sound produced by the magnetic clutch, which is heard every time the ECU switches it on and off.

Option 3

The compressor should be replaced with a new one.

Warning Only if the compressor is fitted with a clutch should it be converted (see below).

How to Locate the Displacement Control Valve

The position of the displacement control valve is seen in Fig. A. (DCV). A circlip is used to hold it in place. To take it out, just unscrew the circlip from the valve and pull it out. The displacement control valve is shown in Fig. B, which has been removed.

Option 1: Adjusting the DCV (Displacement Control Valve), If Adjustable

Note:On some vehicles, the displacement control valve is easily accessible and may be pulled out without the need to remove the compressor from the vehicle. You may need to remove both the compressor and the DCV if yours is different from the one shown here.

Option 2:Converting the Compressor to Run as a Fixed-Displacement Type

To begin, unscrew the circlip that secures the control valve in place (Fig. A.) 2 – Clean the dirt from the area around the top of the valve, then add a little amount of oil and carefully pull it out. Because of the tight fit of the O-rings within, it may be difficult to completely remove the valve. 3. Take the filter out of the equation (Fig. B). 4: Tighten (turn clockwise) the lug screw for a couple of revolutions with the help of a hex key (Fig. C). No specific number of rotations is required, however it is crucial to remember that the greater the number of clockwise turns performed, the closer the compressor is to operating as a Fixed Displacement Compressor (similar to older types of compressors).

All you want is to keep the compressor’s pumping action from deteriorating prematurely, which would result in a loss of cooling in the car’s interior.
Sixth, swap out the old O-rings for new ones that are identical in size to the originals.
7.
If you have removed the compressor, reinstall it and charge the system according to the manufacturer’s recommended charging procedure for variable displacement compressors (see section 2).
Otherwise, the issue has been resolved.
You may have over-tightened the adjustment lug screw, causing the compressor to behave as if it were a fixed displacement compressor, if the compressor fails to change its displacement automatically and the compressor is being turned on and off by the ECU through the compressor’s clutch.

Option 3.Replacing the Compressor

1. Remove the circlip that holds the control valve in place (Fig. A.) 2. Clean the dirt from the area around the top of the valve, then add a little amount of oil and carefully pull it out. Because of the tight fit of the O-rings inside the valve, it may be difficult to completely remove it. 3. Take out the filter (Fig. B). 4. Tighten (turn clockwise) the lug screw for a couple of revolutions with a hex key (Fig. C). No specific number of rotations is required, however it is crucial to remember that the greater the number of clockwise turns made, the closer the compressor is to operating as a Fixed Displacement Compressor (similar to older types of compressors).

All you want is to keep the compressor’s pumping action from deteriorating prematurely, which would result in a loss of cooling in the car’s interior.
Remove the filter and reinstall it.
Replace the O-rings with new ones that are the same size as the previous ones and tighten them down.
7.
If you have removed the compressor, reinstall it and charge the system according to the usual charging procedure for variable displacement compressors.
Run the air conditioning system to ensure it is working properly.
Then re-adjust the control valve for a few more turns and run the test once again to see whether there is still a premature drop in the compressor’s pumping action that is resulting in insufficient cooling.
If this is the case, go return to Step 1 and repeat the process.

how-to-select-the-correct-refrigerant-control-valve-for-your-variable-displacement-compressor.htm

When your wife arrives home and says, ‘Honey, the air conditioning in my car isn’t functioning,’ you respond, ‘OK darling, I’ll look into it.’ After that, you get in your car and start driving down the road as ice cubes are shooting from the vents. You return home, perplexed, and proceed to tell her that she most likely had the switch in the incorrect position and that everything is fine.until it happens again, and this time she confirms that everything is turned on, and the air conditioning system begins to operate intermittently or marginally at best on a regular basis.

You drive the automobile to the dealership, where the salesperson informs you that your compressor is weak and has to be replaced.
While your pulse rate is rapidly increasing and your blood pressure is rapidly decreasing, you check online and discover that this is a typical problem with Volkswagen air conditioning systems, and that there is often an affordable repair for it.
In a variable displacement compressor, the stroke of the pistons is varied by adjusting the angle of the wobbling plate, which is located between the pistons.
It is possible to explain how they operate in an extremely simplistic manner by saying that they leak pressure internally from the high side to the low side and utilize that pressure to adjust the angle of the wobbling plate.
If we adjust the angle of that plate, we can modify the stroke of the piston, which in turn raises or reduces the displacement while the piston is under stress, which is simple to understand.
As a result, the compressor only pumps as much as is required.
In the mechanical valve, a diaphragm measures the pressure on the low side of the valve.
A port opens to allow pressure in the housing to be vented to the suction side of the compressor head through the compressor head.
The electrical valve performs the same function as the mechanical valve, although in a somewhat different way.
The computer analyses this information and regulates the duty cycle of the valves, which in turn regulates the pressure in the housing and the stroke of the piston.

This is performed through the use of ‘PWM,’ which stands for Pulse Width Modulation. In layman’s words, this means that the valve is controlled by a pulse rather than a continuous current. As a result, the valve will cycle on and off frequently within a short period of time.

So How Do I Know Which Variety I Have?

In most cases, if you’ve come this far, it’s because you’ve discovered that your car is equipped with a variable displacement compressor, and you’d like to learn more about how to identify it and decide whether or not it is the source of your problem. Mechanical and electronic control valves are the two types of control valves available. Mechanical control valves can be installed either inside or externally, depending on the application. The external valves are positioned on the back head of the compressor and are kept in place by a snap ring to prevent them from moving.

Simply remove the Freon from the system, remove the snap ring, and replace the valve with a new one.
This will cause it to burst out of the compressor like a bullet and may cause significant physical injury if you do not follow my instructions.
To reach the valve, you must first remove the rear compressor head from the engine.
These valves are often kept in place with a bolt or a snap ring, and they may be removed by using the same procedure as described above for removing an external mechanical valve.
It is possible to have a direct drive compressor with an electronic control valve even when there is no wire coming from behind the pulley and only one wire flowing to the rear of the compressor.
It is imperative that you do not attempt to remove the snap ring or bolt until you are positive that all of the Freon has been completely emptied from the system.

Diagnosis

In most cases, if you’ve come this far, it’s because you’ve discovered that your car is equipped with a variable displacement compressor, and you’d like to learn more about how to identify it and decide whether or not it is the source of your problems. Mechanical and electronic control valves are the two types of control valves that exist. Valve assemblies for mechanical control can be installed either inside or externally. In the back head of the compressor, external valves are attached with a snap ring and kept in place by the same.

The valve may be swapped out by simply taking off the Freon and snap ring.
This will cause it to burst out of the compressor like a bullet and may cause significant physical injury if you do not follow the instructions.
In order to reach the valve, you must remove the rear compressor head.
This type of mechanical valve can be locked in place with either an internal bolt or an external snap ring, and it can be removed using the same procedure as described above for the removal of an external mechanical valve.
Direct-drive compressors with electronic control valves are distinguished by the absence of a wire coming from behind the pulley and a wire flowing to the rear of the compressor.

It is imperative that you do not attempt to remove the snap ring or bolt until you are positive that all of the Freon has been removed from the system. This will cause it to burst out of the compressor like a bullet and may cause significant physical injury if you do not follow the instructions.

Identifying Your Valve

The ‘lookups’ for mechanical control valves are fairly precise in terms of precision. Often, merely knowing the kind and model of compressor you have can allow you to purchase the suitable valve for your needs. There are a few that need the valve to be removed and compared to a picture or a physical match. The Sanden SD7V16 compressor, which is controlled by a mechanical control valve, was used in the older model Volkswagens. It is located internally and requires removal of the back compressor head in order to be installed.

Only one condition applies: the valve plate reeds must be returned in precisely the same position as they were removed, otherwise the compressor would not pump.

Unfortunately, electronic control valves do not have dependable ‘lookups’ like mechanical ones.

Using the example above, you may have two identical automobiles – the same year, model, and engine – as well as several compressors from various manufacturers, ALL WITH THE SAME FOOTPRINT This implies that your Denso brand compressor can be used in lieu of your Sanden brand compressor, however their electronic control valves are different.

A bolt or a snap ring can be used to fasten electronic control valves to their mounting brackets, which are always located on the outside of the valve.

For your convenience, we have built the RCVVALVES.COM Website, which offers huge photos of all of the valves on a single page to aid you with identification.

Web Store.

HOW DO I KNOW WHICH ONE TO BUY?

Physically inspecting the compressor and determining its brand are the initial steps in the process. A number of manufacturers, most notably Volkswagen, will employ a number of different compressor brands for the same vehicle’s model year, body style, and engine. These compressors will have the same footprint and will be interchangeable as whole systems, but the compressor components will not be interchangeable with one another. Example: Two individuals may own identical automobiles in every aspect, with the exception that one vehicle is equipped with a Sanden compressor while the other is equipped with a Denso compressor.

They both have the same physical footprint.
The Sanden’s valve is distinct from the Denso’s valve in that it has a different design.
along with an illustration showing the exposed portion of the valve and the connection A camera phone may be quite handy for this purpose in many cases.
In most cases, a photograph will serve.
Both have the same photographs in them.
For example, Volkswagen and Audi employ a unique connector that is sometimes referred to as aVAAG (VolkswagenAudiG roup) connector.
Following the identification of the connector, the next step is to examine the top (exposed section) of the valve, making note of any unique characteristics and comparing them to our photos.

In contrast, a Denso valve may have a ‘rib’ across the diameter of the valve, which extends from the center of the connection, whilst another Sanden valve may have a rectangular post with the shorter sides rounded We have done our best to depict these characteristics in our photographs, and while they are not 100 percent failsafe, they will assist you in identifying your valve with a decent degree of certainty.

If you are still unsure about the valve you require, please do not hesitate to contact us and send us photographs of your valve.
In the worst-case situation, you may be required to remove the valve in order to adequately identify the problem.
This will cause it to burst out of the compressor like a bullet and may cause significant physical injury if you do not follow my instructions.
Remember that the length dimension is measured from the top of the valve that lies under the snap ring to the tip (bottom) of the valve (not including the snap ring) (part inserted into the compressor).

If all of these criteria are met, you have most likely picked the proper valve. Again, to stress, PLEASE DO NOT HESITATE TO CONTACT US FOR ASSISTANCE. That is exactly what we are here for.1800 365 3516. More information will be provided in the near future.

A/C Compressor Control Valve explained

A large number of air conditioning compressors in current automobiles have variable displacement technology, which means that the compressor is always powered by the engine. This causes the engine controller, also known as the ECU, to provide modest current to the Compressor Control Solenoid Valve, which allows the engine controller to alter how much refrigerant the compressor pumps, which can range from 0 percent to 100 percent. In order to provide optimum cooling and comfort on hot days, the compressor pumps a large amount of refrigerant even while it is at idle.

This works effectively at higher engine rpms and colder outside temperatures, lowering the stress on the engine and the amount of gasoline it uses in the process.
Some of the following signs of failure may be experienced: – A/C performance varies from very cold to very little or no cooling at times.
It is important to note that, in the majority of situations, just the Control Valve has to be replaced, rather than the entire compressor.
So, what causes the control valve to malfunction?
This is the most typical type of mechanical failure.
(It is not necessary to replace) You may arrange this repair for your automobile in Perth, WA, by completing an Online Booking and selecting the option ‘Inspection.’ You can also leave a comment with further information regarding the repair that is needed.
This is a regular failure in Valeo, Sanden, Zexel, and Denso compressors that are used in Volkswagen automobiles, among other manufacturers.

The variables of variable displacement A/C compressors

Flowers bloom as a result of April rains, and with with the flowers come various weather-related factors such as heat, humidity, and pollen! For many drivers, this means that getting their vehicle’s air conditioning to operate at peak performance is not a choice.

it’s a need! With so many modern automobiles now employing variable displacement air conditioning compressors, it is imperative that we become more knowledgeable about how they operate and how to detect any problems.

Figures 1A, 1B and 1C – This Delphi V5 (Variable Displacement – 5 Cylinder) compressor’s wobble plate (1A) is connected to the 5 pistons.As the drive belt via the engaged compressor clutch turns the shaft, the angle the shaft rotates at is controlled by the pressure valve (1C).The controlled movement of the flexible wobble plate is guided along a rod with a brass bushing (1B).When lubrication problems occur as a result of improper oil balancing (when a new compressor is installed) or a large leak that causes oil loss this bushing’s brass particles end up circulating within the A/C system.If you see brass in a screen or filter – it came from the compressor which has either failed or is nearing failure. (Figures courtesy of Delphi Technologies)

Figure 2 – In reduced stroke position, the bellows extends causing the ball valve to open. The suction orifice closes, discharge gasses flow to the compressor’s crankcase and the compressor de-strokes.In full stroke mode, the bellows compress allowing the ball valve to seat.The suction orifice opens allowing compressor crankcase gas to flow to suction resulting in the compressor going to full stroke.

What is the purpose of varying compressor displacement? An A/C component known as a POA (Pilot Operated Absolute) valve that I remember working on when I was much younger kept the evaporator’s output pressure from dropping too low. We are all aware that when evaporator pressures are too low, the evaporator’s temperature is also too low, resulting in ice formation on the evaporator fins due to condensation. Because an iced-up evaporator will not let air to flow through its fins, the passenger compartment will begin to heat up as a result.

In other cases, OEMs did (back then) what they still do today: they combined an expansion valve with an evaporator temperature switch, which shuts off the compressor clutch relay when the evaporator temperature drops too much below a certain threshold.
This improved fuel efficiency on all save the warmest days, when the compressor was forced to work almost whole time due to the high temperatures.
However, there were certain side effects that were less than desired.
It was a familiar sensation.
As a result, the ‘feel’ of the compressor cycling between 100 percent displacement (clutch on) and 0 percent displacement (clutch off) has become more evident.

More crucially, the variable displacement output of the compressor, paired with a variable expansion valve opening, allows for evaporator pressures to be kept in the sweet spot between not being too warm (causing passenger pain) and not being too cold (causing passenger discomfort) (evaporator freeze up).


Figure 3 – Zero / Low Stroke	Figure 4 – Full Stroke

Newer variable displacement compressors employ a swash plate with a coupling joint as a means of increasing compression. In these pictures, when the pressure in the sump (compressor case) builds, the swash plate (which is seen as the yellow component in these figures) is forced rearward against spring pressure, causing the compressor to de-stroke. When the sump pressure lowers, an opposing spring pulls the swash plate forward again, allowing the compressor to run for a longer period of time. The sump pressures are managed by either a self-regulating valve or a solenoid valve that is controlled by electricity.

Both reciprocating piston designs and non-piston compressor designs (such as the scroll) were first converted to variable displacement operation through the use of a manual self-balancing pressure control valve (Figures 1A, 1B, 1C).
(Figures 3, 4).
Oil maladies are the compressor’s number one adversary.
Adding an excessive amount of refrigerant oil to a system can be almost as detrimental as having an insufficient amount of oil in the system.
Too much oil might be difficult to detect.
For example, just because a compressor is provided with X number of ounces of oil inside does not imply that all of that oil should be left in the compressor prior to installation.
Essentially, you drain the oil from the old compressor and take measurements of it.
Before starting the engine, turn the compressor shaft by hand to ensure that it is properly aligned.
According to fundamental gas principles, the higher the pressure, the higher the temperature.
The other side of the coin to an excessive refrigerant and/or excessive oil charge is a refrigerant charge that is much too low.

An inadequate refrigerant charge (or the use of wrong oil) can result in oil that is present in the system but is not going through the compressor in the manner that it should. This will, in turn, result in the early failure of the compressor.

Figure 5 – Electronic Variable Displacement Compressor Solenoid (GM)

Figure 6 – Toyota Corolla Compressor Drive Pulley with Break Away Face Plate (Photo courtesy of GPD – Global Parts Distributors)

This VDC (Variable Displacement Compressor) electronic solenoid (Fig. 5) from a 2013 Chevy Malibu works in a compressor utilizing a conventional electro-magnetic clutch allowing for a full compressor shut off while the same model year Toyota Corolla’s electronically controlled VDC does not use a clutch.Toyota along with a few other imported OEMs eliminate the need for a compressor clutch by using a 0-100 percent variable displacement solenoid duty cycle.Note the special break away front of the Toyota’s drive pulley (Fig. 6) which allows for a faulty compressor to lock up w/o throwing the main accessory drive belt.

Pressure control valves that are controlled by electricity Newer A/C compressors use solenoids (Figure 5) to control compressor output, which is a concept that is similar to that of electric solenoids that control the flow of oil in an engine with variable valve timing. The solenoid replaces the previous design self-regulating pressure control valve, which is no longer in use. In order to lower the compressor’s stroke, the HVAC controls (which are monitoring A/C pressures) tell the compressor’s solenoid to move the swash plate when the evaporator temperature (and pressure) begins to decline (as the vehicle’s interior cools down) (displacement).

You most likely starting seeing this sort of compressor on vehicles with smaller / lower-powered engines initially, before moving on to others.

The compressor clutch has been deleted in many German and Asian imports, with the electric solenoid of the computer-controlled VDC being used to shut off the compressor when it is no longer needed, rather than using a full movement to zero displacement as previously.

This allows the compressor’s driving pulley to continue spinning even while the compressor is locked up.

Figure 7 – Knowing the how a variable displacement compressor is electrically operated is an essential step in your diagnostic process.Even the most complex schematics can be simplified with colored high lighters.On this late model GM schematic we circled controlling devices (blue), sensing devices (yellow) and controlled devices (green).Red and black are used for main power and grounds and purple is used for a data bus circuit.Note the control circuit to apply the ground for the compressor clutch relay originates at the ECM while the control for the compressor’s variable displacement solenoid comes from the HVAC control module.

Diagnostics of a VDC solenoid While diagnostics on variable displacement compressors employing self-regulating pressure control valves can be difficult, electric solenoids can be checked using a scan tool, which makes them more accessible. Always refer to the vehicle’s wiring diagram (Figure 7) to ensure that you are completely aware of which component in the system controls the compressor’s clutch (if one is utilized) and displacement control solenoid before performing any work. When it comes to diagnosing a malfunctioning A/C VDC solenoid, many people have different ideas about what to do.

If you try to repair the control solenoid of an old and ailing compressor only to have the compressor fail 6 months later, you’re wasting your time.
The solenoid on the Ford Escape shown in Fig.
Always check to see that the solenoid is not shorted or open before attempting more complicated diagnostics with a variable displacement compressor activation tool.
9) measures 13.2 ohms, which is within specifications.

In contrast, if the compressor is not an old, high mileage specimen, and a replacement solenoid is readily available AND the solenoid is easily accessible (Figure 8), many technicians are reporting profitable and successful A/C repairs that are both quicker and less expensive for the customer (Figure 8a).

If you are not familiar with the procedures for monitoring high and low side pressures on variable displacement compressors, you may misdiagnose a low system or other problem when the system is actually operating well.


Figure 10 – Ford VDC solenoid normal low duty cycle – pressures are lower	Figure 11 – Ford VDC solenoid special tool commanding a high duty cycle – pressures are higher

Figure 12 – Researching the acronyms used by Ford on their IDS scan tool was necessary in order to know which DPIDs to look at while diagnosing.Ford calls their VDC solenoid the EVACC – Electronic Variable A/C Control. The varying duty cycle sent to the solenoid to vary the compressor’s displacement has an average current draw.Both duty cycled command (61.17 %) and actual current draw (743 mA) are displayed along with high side pressure (145.87 psi). Knowing the resistance of the solenoid along with the exact voltage level available to the solenoid would give you the expected current draw IF the duty cycle was 100 % using a simple Ohm’s Law equation.(Volts = Amps X Ohms)Since the DPID indicates the duty cycle is just over 61 % the current draw should be 61 % of that expected value.Using data that’s easy to obtain (via the scan tool in this case) and Ohms Law can help you to see if the actual current and expected current are very close.If the actual current is much lower than you calculate – it’s time to see where the excessive voltage drop is in the circuit!

When it’s 72 degrees Fahrenheit and 50% humidity, your RRR machine (or manifold gauge set) may read 60 psi on the low side and 100 psi on the high side, depending on the weather conditions. When using a traditional fixed displacement compressor, you can reasonably conclude that the compressor has a low charge or is underperforming. This reading is normal on a late-model Ford Escape equipped with an electronically-controlled variable differential control (VDC). The proof is nearly always flushed out in a performance test that indicates whether or not the system is cooling, but we’re sometimes inclined to overlook the obvious ‘if it ain’t broke, don’t repair it’ guideline and follow our gauge readings closely (Figures 10, 11).

Considering that some manufacturers will not even allow their factory scan tool to regulate their VDC solenoids, obtaining a specialist instrument (Figures 15 and 16) to ramp up the solenoid’s output to establish exactly what the core problem is would be a good option for you.
According to Figure 13, the high side pressure is roughly 80 psi with the compressor clutch engaged and the VDC (Variable Displacement Compressor) solenoid set to the highest possible setting (89 percent).
It’s possible that the solenoid has been stuck in the low stroke position if the answers to the last two questions are ‘Yes.’ According to Fig.
The pressure on the high side is 142 psi.
A few of the most common variable displacement compressor solenoid activation instruments on the market are the Four Seasons, GDP, and Airsept (see Fig.
Additionally, the Airsept EVC-2 has two temperature probes that can be connected to high and low side component tubing to allow for a quick check to see if the compressor’s displacement is truly changing.
16) is an OEM tool that was developed exclusively for Ford.

2011 Hyundai Sonata Air Conditioner Technical Service Bulletins

Service Bulletins for Hyundai Sonata Air Conditioners for 2011. ComplaintsRecalls TSBsInvestigations MPG-Ratings for Safety Schedules for preventative maintenance Price◂▸ 5NP-B3Q3X-07TSB Number:10115697NHTSA Number:10115697 TSB The date is June 7, 2017. The file was last updated on August 17, 2017. Component that has failed: Equipment: Appliance: Air Conditioner Summary: As a result of this advisory, new servicing procedures are provided to aid in the diagnosis of cars equipped with variable displacement air conditioning compressors that are controlled externally (ecv).

This TSBTSB Number:5NP-D4B5F-04NHTSA Number:10110929 has the following identifiers: TSB Date: Thursday, March 14, 2017 The file was last updated on August 10, 2017.

This condition may create interference with one or more of the internal flaps that control the air conditioning system. It may be discussed at ForumView. This is a TSB.

More Hyundai Sonata Air Conditioner Service Bulletins of Other Model Years

Among the most recent years are: 2018, 2014, 2013, 2012, 2009, 2005, 2004, 2003, 2002, 2001, 2000, 1999

More Air Conditioner Service Bulletins of Other 2011 Hyundai Models

The following items are included: ABS Wheel Speed Sensor (3)
Adaptive Mobility Equipment (16)
Anti-Lock Braking System (1)
Automated and Adaptive Steering Motor and Actuator (1)
Automated Transmission (17)
Axle Assembly (1)
Axle Shaft (1)
Back Over Prevention (1)
Battery (1)
Battery Cable (1)
Brake (4)
Brake Light Switch (1)
Cooling Fan (1)
Cooling Hose, Line, Piping, and Fitting (1)
Door (1)
Electric Power Steer