Guys ... I saw many people posting questions regarding their car airconditioners..so i decided to do a bit of research and collect some viable tips which wud help u all during the unbeatable summer...
***** Article 1 *****
Things to Check Under the Hood
Drive Belt
A drive belt makes the air conditioning compressor turn, and that keeps the refrigerant circulating like it should. If the belt is worn, stretched or cracked it can slip or break--which stops the compressor. When that happens, circulation stops and the air conditioner quits cooling.
The drive belt and compressor are sometimes hard to find. Many new vehicles have covers and components that hide the belt and the compressor. The next time you take the vehicle to the shop, ask the technician to show you where both are located.
Air Conditioning Condenser
The air conditioning condenser is located in front of the vehicle's radiator and looks similar to the radiator. Refrigerant runs through the condenser, which has cooling fins. Air flows across the fins and removes heat from the circulating refrigerant.
If the cooling fins become damaged or plugged up with debris, air flow is restricted--and that means heat can't be removed properly. Restriction can also cause the vehicle to overheat. Periodically check the fins to make sure they are clean and in good condition.
Things to Check Inside the Auto
There aren't any visual checks to perform inside the vehicle, but there are some signs to watch for that will alert you to developing problems.
Signs of Air Conditioning Problems
* Wet carpeting on hot, humid days can indicate a clogged air conditioner drain. When the drain is working correctly you'll see a good amount of water dripping to the pavement under the vehicle after you park.
* A vibration or abnormal noise when the fan is on could indicate debris in the blower fan (mice like to make nests in fans).
* A reduced amount of air coming out the vents, especially if it happens after driving for awhile, might mean the air conditioner's evaporator is freezing up.
* A musty or mildewy odor when the fan is first turned on, or all the time when the system is running, can indicate that mold or mildew is growing in the evaporator box.
You can reduce the buildup of mold and mildew by turning the A/C recirculation switch off when you park the vehicle. If your vehicle doesn't have a recirculation switch, turn the A/C switch away from the "Max Air" position when you park.
Some vehicles will still develop a musty odor--even when you take these steps. Many service departments offer a cleaning procedure for the evaporator.
A Few More Auto Air Conditioning Tips
* When you get into a hot car, roll your windows down a little for the first few blocks. If you have a recirculation button, make sure it's turned off. After the hot air is gone, turn recirc on to get the most out of your system.
* We're all concerned with fuel mileage, but modern auto air conditioning systems are pretty efficient. Turning the A/C off results in minimal gas savings.
If you discover a problem, take the vehicle to a trusted technician.
Source : http://trucks.about.com/od/recallsmaintenance1/a/airconditioning.htm
Article 2 by Mobile Airconditioning Society.
MACS Recommended Air Conditioning Inspection and Preventive
Maintenance Procedures
The Mobile Air Conditioning Society (MACS) Worldwide recommends that motorists have their air conditioning systems inspected annually (or whenever a problem is firstnoticed) using the following inspection points and procedures, and have required
preventive maintenance performed. Proper and regular preventive maintenance for the A/C system contributes to effective and efficient operation and helps to prolong component life, possibly helping consumers to avoid future failures and more costly repairs.
1. Inspect the compressor drive belt for fraying, cracks, glazing, etc.
2. Inspect the flexible hoses and metal lines for signs of leakage or damage.
3. Inspect the compressor for signs of possible shaft seal leakage.
4. Inspect and clean the front of the condenser. The debris that builds up between the fins can raise the head pressures, create engine-overheating problems and that not only affects
performance but also can cause slipping of the A/C compressor clutch. If the vehicle has a minimal grille inlet and obtains the cooling air from the ground below the vehicle, raise it on a lift and inspect underneath. Check air dams and seals for integrity and proper
operation. If there's through-the-grille breathing, look between the grille bars with a flashlight. Note that you may have to remove the grille for access. If there's a gap between the condenser and radiator, it may have a road-film buildup and even leaves and grass between the parts. Washing that out can be very helpful. Oil stains on the condenser core may indicate the presence of a leak and will require further inspection.
5. Check operation of all fans in accordance with manufacturer specifications.
6. Test the travel from cold to hot of the blend-air or temperature door operation to assure that the door is properly traveling and seals at both hot and cold end of travel.
7. If the system has a heater control valve, check that it is functioning properly.
8. Check to make sure that the air selection door moves to both the outside air and recirculation (max) travel positions.
9. If the vehicle has a cabin air filter, check to see if it requires replacement.
10. Check to see that both the A/C system service valve caps are installed. These are the primary seals to seal the refrigerant system and a new SAE tandard specifies that the caps be tethered to the service valve. In the meantime, everything out there doesn’t have
the tethers, so check and replace, if missing.
11. Check engine idle speed stability. Poor idle conditions can be the result of such things as plugs, wires, air filter, exhaust gas recirculation valve, etc. If the idle remains rough, determine the cause. The engine power train computer may disable the A/C when idle is rough or falls below a specified RPM. Also, if a "Check Engine" light is illuminated, this should be diagnosed prior to A/C system service.
12. At both idle and high engine RPM, turn on the A/C and see if the clutch engages smartly. If it doesn’t, follow the recommended diagnostic procedures.
13. a. Identify refrigerant purity within the system.
Air contamination or refrigerant cross-contamination may greatly affect system operation and performance.
b. Do an A/C performance test.
The correct procedures vary slightly; so if you plan to use the vehicle maker’s specifications, follow the procedure to the letter.
14. The importance of proper refrigerant charge and how to determine it is as critical to the expected life of the compressor as it is to the comfort of the vehicle occupants. Since the lubricant is carried by the refrigerant, it is important that the proper refrigerant and lubricant charges are in the system. A low refrigerant charge resulting in inadequate lubricant flow affects the compressor because it may be starved for lubricant, but the problem might not be immediately evident to the owner. Eventually they may notice a decline in cooling, but by that time the compressor may be damaged.
15. Establishing System Refrigerant Charge
Orifice Tube System
In the case of an orifice tube system, a general indication of normal system refrigerant charge can be obtained by measuring the evaporator inlet (after orifice tube) and outlet pipes. A completely charged orifice tube (a.k.a. flooded evaporator) system should have the same temperature — or not more than a few-degree difference — at the inlet of the evaporator (behind the orifice tube) and the outlet of the evaporator (between the evaporator and before the accumulator). To make this test valid, the system should be stabilized and under significant load: high blower, windows open and a Max Cold setting.
(It should be noted that on some systems, this does not assure proper refrigerant charge due to refrigerant distribution problems within the evaporator core under high cooling
loads.)
If the temperature differential across the evaporator inlet and outlet pipe is excessive (varies more than two degrees), professional service is required.
In today's A/C systems, the correct refrigerant charge is more important than ever. System pressures readings do not identify the amount of refrigerant in the system. Simply adding refrigerant to a system ("topping off") is not acceptable.
If it is determined that the system is undercharged or empty, the correct professional servicing practice is to remove the refrigerant with recovery equipment and charge the correct amount of refrigerant into the system.
Expansion Valve System
This evaporator inlet and outlet pipe temperature procedure does not apply to systems that use an expansion valve (TXV) since the purpose of the valve is to control super heat settings in the cooling coil. Therefore, temperature of the evaporator inlet and outlet pipes
will vary.
Source : http://www.macsw.org/pdf/PM.pdf
Article 3: Automotive AirConditioning Information Forum
Tip 1
Poor system performance could be faulty reed valves. A hissing sound from the compressor immediately after shutdown indicates high side to low side pressure leakage. To check this, attach manifold gauges and turn compressor on. Readings showing lower than normal discharge pressures and high suction pressures or a rapid stabilization of gauge readings shortly after shutdown indicate leaking reed valves or head gasket.
Tip 2
While performing any service work on a vehicle always inspect the condenser's surface area. Dirt, bugs and any other debris will restrict air flow therefore reducing the condenser's ability to dissipate heat properly. It is recommended that on long haul trucks, off road equipment (construction, logging, mining etc) and agriculture machines that this be done on a regular monthly basis. Also be careful not to bend or damage the fins in the process of cleaning.
Tip 3
Did you know that...the refrigerant oil color can often provide us with some idea of the compressor and internal system conditions? Black Oil indicates carbonization caused by air (moisture) in the system. Brown Oil indicates copper plating caused by moisture in the system. Grey or Metallic oil indicates bearing wear or piston scoring. Piston scoring may be attributed to high head pressure caused by system moisture.
Tip 4
When replacing the clutch assembly always make sure to re-install the snap rings properly. Snap rings have two sides, one is flat and the other beveled. The beveled side should always go to the outside to ensure proper fit.
Tip 5
Always flush the A/C system to remove any contaminates and replace any parts that cannot be flushed. It is also a good practice to use inline suction filters to help catch any foreign material.
Did you know?
The most common reason a replacement compressor fails (new or remanufactured) is caused from contaminates from a previously failed compressor.
Tip 6
When working with either PAG or Ester oils always be sure to keep the container capped when your not using. The chemical makeup of these types of oils will absorb moisture and can create a problem in the a/c system later.
Tip 7
Heat is present everywhere. A/C systems are designed to remove heat from one place to another. There are three laws that must be present for refrigeration systems to exchange heat from inside a passenger compartment to the outside atmosphere. First of all, Heat travels to cold or less heat. Second of all, Condensation releases or dissipates heat. Last, Evaporation captures heat. Using the laws of refrigeration in a closed loop circuit of components, temperatures can be controlled. I.E. Automotive a/c system.
Tip 8
A/C systems can be contaminated with metal particles from the normal wear of the compressor and tiny amounts of water moisture. Contamination can cause a system to fail. Protection against contamination is provided by the filter screen on the Expansion Tube and the desiccant in the bottom of the dryer or accumulator. Other forms of contamination may be the wrong kind of oil, wrong kind of liquid charge or other material that will interfere with the cooling system. Almost 100% of moisture is normally removed from the system when it is evacuated prior to installing (R12 or R134a), but flushing the entire system will be the only way to remove any particles.
Tip 9
When either installing a new a/c system or doing a service job always make the drier the last component replaced before evacuation and recharge. The desiccant in the drier absorbs moisture and will decrease performance and create a problem to the system at a later date. Moisture and refrigerant when combined creates an acid and will damage the internal parts of the a/c system.
Summer Checkup, what can you do?
There are different types of checks that can be done on the ac. Most checks include the following. Visual inspection of the compressor and lines for signs of A/C oil leakage, noise inspection, belt inspection, testing the low and high side pressures for the proper amount of refrigerant, A/C output vent temperature test, inspecting and cleaning drain tube, inspection and confirmation of proper fan operation.
Tip 10
Things to do and look for when draining oil from a compressor...
1) At what ambient was the comp drained at? Hot=more drained oil, Cold=slow/ less oil.
2) Were the ports / caps removed to prevent a vacuum?
3) Was the oil drained and measured from the cylinder head as well as the compressor body?
4) Please remember that depending on the temp at time of draining that aprox 1/2+ oz will remain in the compressor.
5) When the compressor was drained was the compressor crank turned or rotated? 6) How long was the compressor drained?
Did you know?
Some new compressors can leave the factory without an oil charge but checks and balances in most manufacturer's processes at several different stations that check precise weights of individual and pallet compressors and electronic monitors at the filling station make it hard to pass through. To be on the safe side always check your new compressor for oil.
Tip 11
What's the musky smell out my vents? The first component to check is the drainage tube. If the tube is blocked it will trap the water and cause mildew to set it. Some vehicles have a foam type material that surrounds the evaporator. If this foam becomes wet from condensation or other means then it also has the tendency to cause the musky smell. There are procedures that can be done to eliminate the problem.
The second component to check would be the a/c cabin filter.
For years, Import vehicles have incorporated these cabin filters. Cabin Filters work in the same manner as a home cabin filter. If dirty can give a foul odor and poor air flow. Most auto manufactures recommend to replace every 10 to 15K miles. Most cabin filters are located behind the glove box in the evaporative box (see owners manual for location and replacement instructions).
Tip 12
While performing any service work on a vehicle always inspect the condenser's surface area. Dirt, bugs and any other debris will restrict air flow therefore reducing the condenser's ability to dissipate heat properly. It is recommended that on long haul trucks, off road equipment (construction, logging mining, etc) and agriculture machines that this be done on a regular monthly basis. Also be careful not to bend or damage the fins in the process of cleaning.
Source : http://www.autoacforum.com/categories.cfm?catid=20
Over all Tips and Warning
* Most air conditioning repairs are best done by a professional. If it is a problem that you don’t understand, your best bet is to take it to a mechanic.
* To keep your air conditioner in good shape, manufacturers suggest running it 10 minutes a month, even in the winter months, to keep it running smoothly.
* Be careful when taking things apart inside your car to look at the air conditioning system. There are many moving belts and sharp edges that can hurt you.
Cheers
