REQUIREMENT
1). Creation of comfortable environment
a). Controlling of temperature
b). Controlling of humidity
c). Removing of particles
d). Proper air circulation.
f). Removing of unpleasant odors.
2). Creation of healthy environment.
a). Prevention of microbial growth
b). Introduction of cleaned fresh air.
3). Efficiency
a). Power saving
b). Fuel saving

4). Environmental protection
a). Reduction of emission.
b). Avoid releasing of refrigerant.
c). Avoid releasing of oil mist and other service chemicals.
1.
Controlling of temperature and humidity is done by the refrigeration circuit.
It has to be maintained properly to obtain the required conditions.
Particles are trapped by the cabin air filter.
Particle retention capacity should be at least 400g/sq.m
Proper air circulation by fan blower unit is required to maintain uniform
temperature and required RH inside the cabin.
It also helps to take stale air away and move fresh air towards the occupants.

2.
Conducive atmosphere is available inside the evaporator for microbial growth.
i.e Moisture, temperature, darkness
Microbial growth on the surface of the evaporator causes the unpleasant odors inside the cabin.
Disinfection of these surfaces are required to proper hygienic conditions inside the cabin.
Expelling of stale air and introduction of cleaned fresh air is required to reduce the level
of carbon dioxide and increase the level of oxygen.
3.
In mobile air conditioners compressor is driven by the engine.
If the compressor is not running smoothly, there will be additional load on the engine.
It will decrease the engine pulling power.
It will increase the fuel consumption as well as atmospheric emission.
Proper lubrication will eliminate these problems.
Need to use recommended oil by the vehicle manufacturer.
Manufacturer has provided the oil code.
It has to be matched with the oil manufacturers oil code.
Oil manufacturers code denotes the type of chemical and ISO viscosity.
PAG (Poly Alkylene Glycol) is the recommended lubricant for mobile air conditioners.
The viscosities are ISO 46, 100, 125 and 150.
4.
If the mobile air conditioner is well maintained fuel consumption and atmospheric
emissions will be less.
To prevent Global warming and Ozone depletion, refrigerant must not release to the atmosphere.
Refrigerant can be recovered recycle and reuse.
Recovered refrigerant must be recycled before use again.
If not, the system will be contaminated and will not function properly.
While flushing, chemicals and oil mist must not be released to the atmosphere.
Need to flush with closed loop flushing machines.

REPAIRING OF MOBILE AIR CONDITIONERS
If air conditioners are well maintained, failures will be minimal.
Periodic maintenance and services are required to minimize the possible break downs.
There are four types of failures.
1). Failures due to leakage of refrigerants.
2). Failures due to defective mechanical components such as compressors.
3). Electrical failures.
4). Failures due to use of incorrect spare parts, lubricants and impure refrigerants.

1.
Refrigerant could be leaked as follows.
a). Due to loosened joints nuts etc.
b). Due to corroded components.
When it is noticed that there is a refrigerant leak, first thing is to locate the leaking point.
Major leaking points could be identified by visual checking for oil patches etc.
If there is some refrigerant remain in the system, electronic leak detector could be used to locate the
leaking point.
If the refrigerant has lost completely, it is necessary pressurize the system with dry nitrogen.
It is necessary to pressure the system using leak testing pressure gauge.
High side and low side should be pressured according to the working pressure.
Test pressures vary with the type of refrigerant and the working pressures.
Soapy water or suitable foaming agent could be used to locate the leaking points.
When there are minute leaking points, fluorescent dye with UV lamp could be used to

locate the leaking points.
Once leaking points are repaired, it is necessary to pressurize the system again and test for
leaks to ascertain that the leaking points are repaired to prevent the leakages.
After using dry nitrogen for leak testing, it is necessary release dry nitrogen completely.
If not remaining dry nitrogen will lead to give excessive high pressure while working.
Compressed air should not be used for leak testing as they can contaminate the system.

2.
When mechanical failures occur, components like compressors, expansion valves,
Charging valves, rubber O rings, belts, bearings should be checked and repair or replaced.
Used or sub-standard components must not be used, in any circumstance unless brand new components are difficult to find.

3.

Electrical failures could occur due to defective motors, fuses, relays, thermostats,
PCB’s, clutch coils, pressure switches, sockets and connecting cables.
They need to be tested with proper testing equipment and repair or replaced.

4.
If pure refrigerant is not used, proper cooling could not be achieved and fuel consumption
may go up. Therefore, it is necessary to choose the correct and pure refrigerant.

Following guidelines will help to find the correct and pure quality refrigerant.

Look for manufacturer’s website, QR code etc. on the packing
Search the website and ascertain that it is genuine.
Use the QR code reader to ascertain the authenticity.
Look for brand registration certificate
Look for independent laboratory analysis reports.
Checking with the manufacturer will help to find the authentic source for purchasing.

Lubricant also very important as well as the refrigerant.
Most of the lubricants in the Sri Lanka market are not genuine.
They are not consisting with approved chemicals.
Therefore, following guidelines need to be considered.

No compressor manufactures produce lubricants
Compressor manufacturer provides their oil product codes.
Need to match the compressors manufacturers product code with the oil manufacturers product code.
(Vehicle manufacturer’s oil code – ND8 Equivalent oil manufacturers code /chemical name – PAG 46)
(Compressor manufacturers oil code – BSE 32 Oil manufacturers code RL 32H.)
Chemical composition and the ISO viscosity grade need to be verified from the manufacturer’s web.
Mobile air conditioners use PAG oil.
Other air conditioners use POE and PVE lubricants.
Refrigeration systems use POE lubricants.
Majority of the oil in the market are not genuine products.
Some have copied famous brand names.
But when check in the relevant websites, differences can be identified.
There are no websites, QR codes and postal addresses printed on the packings of the fake products.
There are some false websites are printed on the packings.
They can be verified through internet.
These fake oils will increase the fuel consumption in vehicles and electricity bill on other equipment.

Guidelines to identify the genuine lubricants.

Look for website, hologram, QR code etc. printed on the packing
Search the website and ascertain that the lubricant is genuine.
Use the QR code reader to ascertain the authenticity.
Some false web address and QR codes are printed on the packing
Therefore, always search for the website in the internet to verify.
Use QR code reader for verification.

REFRIGERATION CYCLE AND SYSTEM COMPONENTS

TROUBLE SHOOT MOBILE AIR CONDITIONING

AC COOLING PROBLEM?
The most likely cause of an automotive air conditioner cooling problem is no refrigerant in the system. If the refrigerant has escaped past a leaky compressor or O-ring seal, leaked out of a pinhole in the evaporator or condenser, or seeped out through a leaky hose, the leak needs to be identified and repaired before the system is recharged.
On many systems, the compressor will not turn on if the refrigerant is low because the “low pressure safety switch” prevents the compressor clutch from engaging if system pressure is low. This protects the compressor from possible damage caused by a lack of lubrication.
One of the first things you should check, therefore, is compressor engagement. If the compressors magnetic clutch is not engaging when the A/C is turned on, the problem may be a blown fuse or a wiring problem. If the fuse is blown, replacing it may restore cooling temporarily. But the underlying reason for the fuse blowing in the first place needs to be identified and corrected to prevent the same thing from happening again.
If the magnetic clutch is receiving voltage but is not engaging the compressor, the clutch is defective and needs to be replaced. If there is any evidence of leakage around the compressor shaft seal, the seal should also be replaced.
If the clutch works but fails to turn the compressor (the belt may squeal in protest!), the compressor has seized and needs to be replaced.
Compressor failures are usually the result of loss of lubrication, which in turn may be due to low refrigerant in the system, a blockage (such as a plugged orifice tube which prevents refrigerant and oil from circulating to the compressor), loss of lubricant due to leaks or improper service procedures (not adding oil to the system to compensate for oil lost through leakage or component replacement), or use of the wrong type of lubricant.
R-12 systems require mineral oil while R-134a systems require various types of PAG oil or POE oil. Using mineral oil in a newer R-134a system can cause serious lubrication problems as can using the wrong grade (viscosity) of PAG oil. Always follow the vehicle or lubricant manufacturers compressor oil recommendations.
The next thing you should check when troubleshooting a no cooling problem is system pressure. For this, you need a set of A/C service gauges. Attach your service gauges to the high and low service fittings. If both the high and low side pressure gauges read low, the system is low and needs recharging. But before any refrigerant is added, check for leaks to find out where the refrigerant is going.

AIR CONDITIONING PROBLEM: REFRIGERANT LEAKS
All vehicles leak some refrigerant past seals and through microscopic pores in hoses. The older the vehicle, the higher the rate of seepage. Newer vehicles have better seals and barrier style hoses so typically leak less than a few tenths of an ounce of refrigerant a year. But system capacities also tend to be smaller on newer vehicles, so any loss of refrigerant will have more of an adverse effect on cooling performance.
Various methods can be used to check for leaks. The telltale oil stains and wet spots that indicate leaks on older R-12 systems are less apparent on the newer R-134a systems because PAG lubricants are not as “oily” as mineral oil. This makes it harder to see leaks.
Leaks can be found by adding special dye to the system (available in pressurized cans premixed with refrigerant), an electronic leak detector, or

plain old soapy water (spray on hose connections and watch for bubbles — requires adding some refrigerant to system first and turning the A/C on). Once you’ve found a leak, repairs should be made prior to fully recharging the system. Most leak repairs involve replacing O-rings, seals or hoses. But if the evaporator or condenser are leaking, repairs can be expensive.

POOR COOLING PERFORMANCE
Diagnosing an A/C cooling problem is best done by connecting a gauge set to the high and low pressure service fitting on the system. Though poor cooling is often due to a low charge of refrigerant, it can also be caused by many other factors (see chart above).
How to tell if your A/C system needs refrigerant: look at the LOW pressure gauge reading when the engine is OFF. On an 80 degree day, the LOW gauge should read about 56 psi or higher if the A/C system contains an adequate charge of refrigerant. On a 90 degree day, the LOW side reading should be about 70 psi or higher. If the LOW gauge reading is less than this, the A/C system probably needs some additional refrigerant.
Refer to the vehicle manufacturer specifications for normal system operating pressures, and the total refrigerant capacity of the system. Most newer passenger car A/C systems do not hold much refrigerant (14 to 28 oz.), so you don’t want to add too much if the system is low.
AIR CONDITIONER PROBLEM: INTERMITTENT COOLING
An A/C system that blows cold air for awhile then warm air is probably freezing up. This can be caused by air and moisture in the system that allows ice to form and block the orifice tube.
Evacuating the system with a vacuum pump will purge it of unwanted air and moisture. Evacuation should be done with a vacuum pump that is capable of achieving and holding a high vacuum (29 inches) for at least 30 to 45 minutes.
For best performance, an A/C system should contain less than 2% air by weight. For every 1% increase in the amount of air that displaces refrigerant in the system, there will be a corresponding drop of about one degree in cooling performance. More than 6% air can cause a very noticeable drop in cooling performance, and possibly cause evaporator freeze-up.
Air can get inside a system through leaks, by not evacuating the system prior to recharging it, and/or by recharging the system with refrigerant that is contaminated with air. Recovery equipment can suck air into the recycling tank if an A/C system contains air or if the system has a leak. For this reason, the refrigerant recovery tank on recycling equipment must be checked and purged daily. On some equipment, this is done automatically. But on equipment that lacks an automatic purge cycle, tank pressure and temperature has to be measured and compared to a static pressure reference chart.
Some refrigerant identifier equipment can detect air in the system as well as other contaminants. An identifier should be used to check the refrigerant before the system is serviced to prevent cross-contamination of recovery and recycling equipment.
Possible causes of intermittent cooling in a manual A/C system that might be caused by an electrical problem include:

Faulty low pressure cutout switch. This switch prevents the compressor from running if the refrigerant level is low. If the cutout switch is not reading correctly, it can prevent the compressor from coming on.

Faulty compressor clutch. The magnetic clutch on the compressor requires full battery voltage to engage. If the voltage to the clutch is low, or the clutch coils have too much resistance, or the air gap in the clutch is too great, the clutch may not engage to drive the compressor.

Faulty compressor clutch relay. Check to see if the relay is receiving voltage when the A/C is turned on. Also check the relay wiring and ground connections. If bypassing the relay with a jumper wire or routing battery voltage directly to the compressor clutch makes the A/C work, the relay is probably bad.

Faulty A/C control switch. The switch may be worn and not making good contact when it is turned on.
Some possible causes of intermittent cooling (or no cooling) on automatic A/C systems include all of the above, plus:

A problem in the control module or control head (this usually requires using a dealer scan tool to read fault codes and perform self-diagnostics).

A bad temperature sensor (an ambient air temperature sensor, interior air temperature sensor, evaporator temperature sensor, or sunload sensor). Again, a factory scan tool is usually required to perform diagnostics on the system.
AIR CONDITIONING PROBLEM: NOISE
Noise from the compressor usually means the compressor is on its way out. But noise can also be caused by cross-contaminated refrigerant (operating pressure too high), air in the system or the wrong type of compressor lubricant.
Noise can also be caused by hoses or other parts rattling against other components in the engine compartment. Check the routing of the hoses, support brackets, etc., to pinpoint the noise.
TROUBLESHOOTING AIR CONDITIONING ODOR
If a vehicles air conditioner blows out air that smells like the inside of old gym sneaker when the A/C is turned on, microbes are growing on the evaporator. Mold likes damp, dark places. Bacteria can also thrive under such conditions. Besides smelling bad, it can be unhealthy to breathe (ever hear of Legionnaires Disease?).
To get rid of the unwanted organisms, various chemicals can be sprayed on the evaporator directly or through the blower ducts or air intake. Many replacement evaporators have a special chemical coating that inhibits the growth of mold and bacteria. The drainage tubes that carry condensation away from the evaporator should also be inspected and cleaned.

A/C FLUSHING
If the compressor has failed, or the system is full of sludge or contamination, the condenser, evaporator and hoses should all be flushed with an approved flushing chemical (such as R- 141b) to clean the A/C system. Flushing can help prevent repeat compressor failures and system blockages by dislodging and cleaning out sludge and debris. Replacing badly contaminated parts such as the condenser, accumulator or receiver-drier and orifice tube or expansion valve is another way to get rid of these contaminants, but flushing is usually a more practical and economical choice. Regardless of which approach you use, the orifice tube or expansion valve should always be replaced when contamination is found.
NOTE: Some types of compressors can be very difficult to flush completely. These include “parallel” flow condensers and those with extremely small passageways. If contaminated, these types of condensers must be replaced to reduce the risk of a repeat compressor failure. Installing an in-line filter is also recommended for added insurance,
When a compressor fails, a lot of metallic debris is often thrown into the system. Most of this debris collects in the condenser where it can cause blockages that reduce cooling performance. If the debris is carried through the condenser and enters the liquid line, it can plug the orifice tube or expansion valve. This can block the flow of refrigerant and lubricating oil causing a loss of cooling and possible compressor damage. Debris can also migrate backwards from the compressor through the suction hose causing blockages in the accumulator or receiver-drier.
Another source of trouble can be debris from old hoses that are deteriorating internally. Tiny flakes of rubber can be carried along to the orifice tube or expansion valve and cause a blockage.
Sludge is usually the result of moisture-contamination. The blackish goo that results can damage the compressor and plug the orifice tube or expansion valve. The moisture-absorbing “desiccant” in the accumulator or receiver-drier is supposed to prevent this from happening. But the desiccant can only hold so much moisture. Once saturated, sludge begins to form. So you should also replace the accumulator or receiver-drier if the system is contaminated, has leaks or must be opened up for repairs.
Another reason for flushing is to remove residual lubricating oil from the system. This should be done when retrofitting an R-12 system to R-134a. It should also be done if the lubricating oil is contaminated or the system contains the wrong type of oil for the application. Flushing out the old oil can prevent oil overcharging, reduced cooling performance and/or lubrication incompatibility problems.
For added insurance after flushing, you can install a high side filter to protect the orifice tube or expansion valve from any residual debris that might still be in the system, and/or a second filter in the suction hose to protect the compressor.
As R-141b is not available, the refrigerant used in the system would be best flushing agent.
It needs to be done with the help of closed loop flushing machine.

This KT-007 machine can recover, recycle, flushing, evacuation, charging refrigerant

and simple fault diagnosis.

CHARGING REFRIGERANT

Before charging refrigerant, it is necessary to make sure that the system has properly cleaned.

Before the installation of a new component such as compressor, condenser or evaporator,

rest of the components with connecting tubes need to be flushed out. If not the remaining

old lubricant in the system can enter in to the new component and contaminate the system.

After the installation of components, it is necessary to verify that the system is leak tight.

Then the system needs to be evacuated until it reaches 28-29 inches.(0.94-0.98bar)

Then hold the vacuum for 15 minutes to ascertain that there are no leaks.

After evacuation lubricant need to be charged according the recommendations

given by the vehicle manufacturer. Required type of lubricant and the it is volume

is printed on a tag. e.g ND 08- 180 ml(This means the lubricant is Poly Alkylene Glycol and

the viscosity is ISO 46 and the volume are 180ml). It is necessary to use graduated oil

gun to charge the precise amount. Before charging oil, it is necessary to ascertain that

there is no oil in the system. (This could be verified when flushing with the flushing machine). If there was oil in the system, it will be difficult to charge the precise volume.

If the oil level goes above the recommended values proper cooling effects can not be

achieved. Therefore, it is necessary to remove all the exhausted oil from the system,

before charging new oil. On the other hand, if old exhausted oil remained in the system,

it will contaminate the new oil as the old oil could be acidic.

After charging the lubricant, refrigerant need to be charged according to the weight

recommended by the vehicle manufacturer. The recommended weight could be found

on a sticker under the bonnet. After charging the correct weight, performance need to

observed using a pressure temperature analyzer.