Introduction on automotive a/c compressor type - Part 2

Continue from my last post, here i gonna talk about Rotary Compressor. As the name suggest, this kind of compressor uses rotary type positive displacement mechanism to compress gases. And the most popular compressor being used under rotary in car a/c can be divided into two, which is Rotary Vane Compressor, and Rotary Scroll Compressor.


Picture show a Rotary Vane in left and Rotary Scroll in right of the Rotary Type Compressor.

Rotary compressor is becoming more and more popular in car a/c system because of the light weight in design, less moving parts compare to reciprocating compressor, and the most importance is the volume it can handle at a time despite its small size is very large compare to reciprocating compressor.

Rotary compressor need less maintenance as long as there is enough oil for lubrication. Also, rotary compressor have less size and weight when compare to a reciprocating compressor. Rotary compressor have a variable volume which it can process at a time, not like a reciprocating that have a fixed volume.

Variable volume make car manufacturer hard to calculate the size of condenser and evaporator, and also the quantity of refrigerant needed to be used in their car. Car manufacturer need to run a long testing on their car to make sure the cooling is enough which will make the production cost higher.

There is several reason why rotary compressor is gaining it popularity. First is, the compressor can handle a large volume of refrigerant which will make the use of refrigerant become less compare to reciprocating compressor. Second, the less moving parts will make the sound and noise produced when the a/c is operation become less when compare to a reciprocating compressor. And final is the lightweight and small size of rotary compressor will make the car lighter and save more space that will benefit in fuel economic.

So this is what i have so far with this 3 kind of compressor. I will talk in detail in future for each compressor. Stay tune for more on.

Introduction on automotive a/c compressor type - Part 1

In this post, i gonna talk about compressor type that is use in the automotive industries. There are several type of compressor that is used in car a/c. Among those, there is two type that is popular  which can category into Reciprocating type and Rotary type.

Reciprocating type can also be called as Piston type compressor. This type of compressor provide excellent and efficient refrigerant movement inside a/c system and it is the most commonly used compressor to this day.

Reciprocating compressor is a fixed volume compressor, it using the movement of piston to create suction and compress to move the refrigerant inside the a/c inlet. This kind of compressor have a certain volume ratio that cannot be altered, hence the volume of refrigerant a piston compressor can suck and discharge at a time is fixed.

The properties of fixed volume provide the car manufacturer an easier way to do the math on how much is the refrigerant, and also how big is the condenser and evaporator needed to be used on their vehicle to provide a adequate cooling for car user.


                                   Picture show piston type compressor with cut away

The picture above is common piston compressor that can be found easily. Many manufacturer comes with their own design, but all with a same basic principle like below:

I not gonna talk bout how is the compressor work in this post, as this is just a introduction to the type of compressor that can be found in car a/c, so i will leave the detail for future.I will talk on Rotary type compressor on my next post. Stay tune for more.

A/C problem troubleshoot - Part 2

This is part 2 of a/c problem troubleshoot. In last post i have talk about cleaning of evaporator, condenser, and changing of cabin air filter and also filter drier. In this post i gonna talk the other problem.

Following the last post, now if the answer to the above question is in a short time, like say in a months, or six months, then the problem will not be very easily troubleshooted. For this kind of problem, then need to ask this question:

1. Do you change any things other than cabin air filter, filter drier on the last service?
2. What is the things you change on last service?

Depending on the answer of this question, the problem will most likely linked to what the answer is. What i mean is, the part/s you change other than cabin air filter and filter drier, is most likely Expansion valve, Blower motor, Cooling motor, Compressor, Evaporator, and Condenser. If you has changed any of the parts i mention above, then the problem is much more serious. I will explain the uses of each part below:

1. Expansion valve - Use to regulate flow of refrigerant into evaporator. It is also use to convert a high pressure refrigerant into low pressure refrigerant.

2. Blower motor - Use to push hot surrounding air inside cabin to go through evaporator for energy transfer.

3. Cooling motor - Use to push cold surrounding air around car to to through condenser for energy transfer.

4. Compressor - Use to making flow of refrigerant so that refrigerant will move inside the a/c system. Also use to giving energy to refrigerant for use in cooling.

5. Evaporator and Condenser - Use as a contact point for refrigerant and surrounding air for energy transfer.

Now, changing of evaporator and condenser usually mean there is a leak of refrigerant through this 2 parts. The leak of refrigerant on this 2 parts will cause the refrigerant level to drop out from the system thus there is not enough refrigerant for a proper a/c to function. Evaporator and condenser will also suffer from condenser oil blockage if the condenser oil level is too high for the a/c system. In this case, either doing a flush on the 2 parts to clear out the oil, or changing the parts directly is a common practice. For leaking case, i will recommend to just change a new parts as it need a very experience person on brazing alloy to braze the hole on the condenser and evaporator.

Blower motor and cooling motor play a major parts in a/c system. This is because if any of this 2 parts fail, then the whole a/c system will suffer from a refrigerant liquid lock, or refrigerant overheat, depend of which parts is failing.

When refrigerant liquid lock happen, the flow of refrigerant will become slow or even totally stop. This happen when the liquid state refrigerant is unable to carry enough energy to boil into vapor (yes, this is what happen when blower motor is failing). And if the liquid refrigerant flow back into compressor, then the compressor will suffer from overheating cause the liquid refrigerant will carry all the compressor oil needed for lubricant out from the compressor (see my post on charging refrigerant in gas or liquid).

When refrigerant overheating happen, the refrigerant is still carry all the energy given by the compressor (this is when cooling motor is the culprit), thus the temperature of the refrigerant can go way up to 80 degree C, at this point, the compressor oil which is in the system will be boiling and cause the oil to break down and becoming an oil sludge which in turn will cause refrigerant flow blockage.

In between the condenser and evaporator is the expansion valve and compressor. Talk bout expansion valve first. This valve will suffer no matter if the refrigerant is having liquid lock or overheating. And if the valve is block due to the problem, then the refrigerant flow will be blocked and stopped, this in turn will make the compressor to break down and broken.

When will the compressor broken? Well it depend on which part of the compressor is failing. Usually when liquid lock is happening, the piston and piston block of the compressor will suffer the most, as this is where the contact of metal occur. Poor lubrication will cause the wall of piston rub against the block body directly then the metal will comes off and the whole compressor will be suffer from metal chip grinding. If overheating is happening, then the valve plate of compressor will suffer from high pressure torture and resulting in broken valve plate thus cannot hold the pressure and back pressure will occur. ( I will have a detail compressor post in future )

Here is the main problem when you change any of this parts, almost all of the a/c shop will not do a whole a/c system flush to save costs and time. Any parts i mention in here, once broken and need replacement, i highly recommend to do a whole a/c flush to flush out all the old compressor oil and debris before installing the new components. If this step is not taken, then the old things is still inside the system and it will cause the new parts to fail once more in a short amount of time. This is why the a/c problem won't be solved no matter what the parts you change. Unless the whole a/c system is replaced include all the hoses and piping.

I have rush trough this troubleshoot parts because if need explaining all the related parts and how to diagnose, then i will take whole a lot of time. I will cover this part 2 again in future after i have all the dedicated post of each components.

Any question can leave in the comment. I will answer it the best i could. Stay tune for more car a/c from me.

A/C problem troubleshoot - Part 1

In this post i gonna talk on how to troubleshoot an a/c problem in car. Many of us will not regularly service our car a/c like what we did on our engine. This is because car manufacturer rarely push to buyer and car owner about the importances to keep a good a/c system as to prevent unwanted break down of a/c. Of cause if compare an a/c to an engine, sure the engine is most important. But as a car owner, who does not want the car to be in good condition the whole time? So we must improve our self to know how to keep a good running car, so that the car does not fail us on the most importance day in our life.

So, the basic of a/c i was talking on my blog, i have gone through all the parts which is used in our car a/c. So if some parts or a part is failing, it will cause problem, then the a/c will not produce nice cold air as it should. Went into a/c shop, we will depend on the technician to tell us what is causing the problem.

Most of car owner is not aware that the detail the technician give is correct or not. They just simply say: ok, just do what you should do.. Then the nightmare begin...A proper done job on car a/c will save a lot of money and time in the long term. But a poorly done job.....It will not only cost you a lot of time, it will also burn a hole through your wallet. Trust me when i say a hole in the wallet.

Then, how should one troubleshoot an a/c problem? Ask your self this question first before making any move:

For new car less than 4 years:
1. Have you done your a/c service?
2. Have you change air con cabin air filter?

For old car more than 4 years:
1. When is the last time you service the a/c?
2. How long have it been after the last a/c service?
3. Have you change air con cabin air filter?
4. Have you change filter drier on last service?

This question need to be ask first, because many a/c problem is cause by a dirty cabin air filter, dirty evaporator, dirty filter drier and dirty condenser. When the cabin air filter and evaporator is dirty, the refrigerant inside evaporator will not have enough contact with the hot air outside evaporator, then the hot air cannot efficiently transfer the heat to the refrigerant (see my post on How does it work).

A dirty filter drier will cause the refrigerant flow be restricted. This will cause a weak flow of liquid state refrigerant into the evaporator. When this happen, there will be not enough refrigerant flow to take away the heat of the hot air around evaporator. Dirty condenser will cause poor effectiveness of the refrigerant to transfer heat to surrounding air before flow into evaporator. A high energy(heat) refrigerant will only be able to carry little energy from the hot air inside cabin thus the air will not be cooled enough.

This kind of problem can be easily solve by having a full a/c cleaning done on evaporator and condenser with new cabin air filter and also new filter drier changed. With a proper cleaning on evaporator and condenser as well as a proper level of refrigerant recharge back into system, the problem of not producing cold air should be okay in at least 2-3 years.

This is part 1 of this post. I will talk bout other problem in second post. Stay tune for more.

How does it work?

How does a/c work actually? Well it work by the mean of heat transfer by utilizing heat radiation transfer theory. In real life, the heat is a source of energy that cannot be seen, but can be feel. This is because heat is a form of radiation energy which we will need a special tool to see it (heat scanner).

Now, how does the a/c work? Easiest way to say, the heat is been absorbed by the evaporator and then it is release to the outside using a condenser. This is the simplest way of explaining. If want to know further detail, then bear with me..


See the number 1 and 2, it show how the surrounding air is being heated and then is cooled

A/C system is a closed system which contain refrigerant as a medium to transfer energy. Heat is a form of energy that can be transfered from one place to another using a radiation wave movement. In a/c, when the refrigerant is been pressurized in compressor, it contain so much energy thus make it hot(heat) to touch. This hot refrigerant then need to transfer its energy to the surrounding when it enter the condenser.



Condenser capture the energy(heat) from refrigerant and then release the energy(heat) by transferring the energy to the surrounding low energy air(lower temperature air). The fan in front the condenser push the surrounding low energy air so that the air can move faster entering and exiting the condenser. The energy in the condenser will travel to surrounding low energy air thus making the air more energize and hot while refrigerant will have less energy and cool down. The refrigerant that is now less energize will become low heat, high pressure liquid and went out from the condenser. At this state, the energy carried by the refrigerant is lower than the surrounding air, as the refrigerant is under high pressure, it will still feel warm to touch even tough the energy(heat) it carry is lower compare to surrounding air.

So the now low energy high pressure liquid state refrigerant will move on to evaporator. Before going into the evaporator, this high pressure, low energy liquid refrigerant will need to undergo depressurization at Expansion Valve first, so that it will enter the evaporator as a low pressure, low energy liquid refrigerant. This i will have future post to talk bout this Expansion Valve. Now i will focus how does a/c work.



This low pressure, low energy refrigerant will capture the energy in the surrounding high energy air while inside the evaporator. The energy in the surrounding air will travel to the refrigerant and release its energy to the low energy refrigerant. This will make the air leave the evaporator as a low energy(cold) air, and refrigerant will become energized and boil into vapor/gas and leave the evaporator.

So it is clear to see, in a/c system, the refrigerant play an important part as it is the only medium for the energy inside the surrounding air to travel to. Thats why when an a/c system is low on refrigerant, the cooling efficiency will drop. But in an a/c system, there is much more things that will cause the cooling efficiency to drop aside from refrigerant alone. I will talk more in my future post.

Charge refrigerant in gas or liquid?

Today topic will be on refrigerant recharge/refill in gas or liquid state. Many car a/c technician will come into this kind of question whether or not the refrigerant should be fill in gas state or liquid state.


There is 2 types of refrigerant already used in car industries, R12 and R134. R12 is banned in 1996 due to the effect it have on our earth ozone layer.

So for starter, refrigerant while still inside can, its continuously appear in gas and liquid form. The liquid will be in bottom of the can while the gas will be aboves the can. The nature of refrigerant which appear in gas and liquid form at the same time is because of the chemical properties the refrigerant have. So the great question begins, should the refrigerant fill in gas state? of liquid state?

This question depends on the charging port location in the car. While the high side port is always far away from the compressor, the low side port is the main factor to the question. Far away the low side port is from the compressor, the safer it is to charge refrigerant in liquid form. This is because, refrigerant in liquid form will carry compressor oil easily, while in gas form, it did not carry the oil.

Farther is the low side port from the compressor will make the refrigerant in liquid form have the time to expand into gas before it reach the compressor. While charging refrigerant, we did not want the compressor oil to directly carry away from the compressor by the refrigerant. Compressor oil is essential to compressor for lubrication, if the oil is carry away from the compressor and leave just a little inside, then the damage already been done after the oil return again to compressor.

This concept is suitable for charging while engine is off or running, because the liquid refrigerant will merge with the compressor oil and moving along when the compressor is working. So charging in gas state is the safest method although it will take a longer time to reach the full amount of refrigerant required by the a/c system.

Simple basic about Automotive A/C - Part 4

Well here comes part 4 of the basic a/c understanding. Here i gonna talk about Expansion valve, Evaporator, and Ventilating Blower (which can also called as Blower in short).


Currently there is 2 kind of Expansion valve that can be found in car a/c, both work in same principle.

Before refrigerant go into the evaporator, it will travel through filter drier, then arrive at expansion valve. In this stage, the refrigerant is in its liquid state, and it will feel warm to touch and is very high in pressure. Here is where the magic happen. The expansion valve will convert this high pressure liquid refrigerant into low pressure refrigerant. The lost in pressure of refrigerant will convert the refrigerant from warm to cold immediately.


Evaporator comes in different pipe arrangement and shape. The left is Serpentine type, while right is Parallel type.

This cold low pressure refrigerant will then enter into Evaporator and it rapidly cool down the evaporator which make the evaporator colder than the surrounding air. The Blower will then blow the hot and humid surrounding air through the evaporator where the hot air will be convert into cold dry air and leave the evaporator. This cold air is what we feel at the ventilating in our car.


Picture at left is how the Evaporator work, and right is what Blower looks like.

The low pressure cold liquid refrigerant will be convert into its gases state while travel inside the evaporator. This low pressure gases refrigerant will be suck back into compressor and the whole process begin again in continuous loop.

So this is all the basic we need to know about automotive air condition. I may have rush to explain this in simple, because many parts cannot be explain in this 4 parts of posts. I will post each of the parts related in their dedicated post. In there i will further explain in detail.

Stay tune for more understanding of our car a/c system.