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Air Conditioning, Page 3 of 3

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Air conditioning safety precautions
See Figure 5

There are two particular hazards associated with air conditioning systems and they both relate to the refrigerant gas.

Figure 5.Check the label on your vehicle to see what type of refrigerant is used.
Check the label on your vehicle to see what type of refrigerant is used.

First, R-12 and R-134a are extremely cold substances. When exposed to the atmosphere, they will instantly freeze any surface they come in contact with, including your eyes. The other hazard relates to fire. Although normally non-toxic, R-12 refrigerant gas becomes highly poisonous in the presence of an open flame. In fact, one good whiff of the vapors formed by burning refrigerant can be fatal. So keep all forms of fire (including cigarettes) well clear of the air conditioning system.

Any repair work to an air conditioning system should be left to a professional.

Do not, under any circumstances, attempt to loosen or tighten any fittings or perform any work other than that outlined here.

System service and repair

It is strongly recommended that the A/C system be serviced by an EPA Section 609 certified automotive technician utilizing a refrigerant recovery/recycling machine.

According to the U.S. Clean Air Act, it is a federal crime to service or repair (involving the refrigerant) a Motor Vehicle Air Conditioning (MVAC) system for money without being EPA certified. It is also illegal to vent R-12 and R-134a refrigerants into the atmosphere. Selling or distributing A/C system refrigerant (in a container that contains less than 20 pounds of refrigerant) to any person whom is not EPA 609 certified is also not allowed by law.

State and/or local laws may be stricter than the federal regulations, so be sure to check with your state and/or local authorities for further information. For further federal information on the legality of servicing your A/C system, call the EPA Stratospheric Ozone Hotline.

Federal law dictates that a fine of up to $25,000 may be levied on people convicted of venting refrigerant into the atmosphere. Additionally, the EPA may pay up to $10,000 for information or services leading to a criminal conviction of the violation of these laws.

When servicing an A/C system you run the risk of handling or coming in contact with refrigerant, which may result in skin or eye irritation or frostbite. Although low in toxicity (due to chemical stability), inhalation of concentrated refrigerant fumes is dangerous and can result in death; cases of fatal cardiac arrhythmia have been reported in people accidentally subjected to high levels of refrigerant. Some early symptoms include loss of concentration and drowsiness.

Generally, the limit for exposure is lower for R-134a than it is for R-12. Exceptional care must be practiced when handling R-134a.

In addition, R-12 refrigerant can decompose at high temperatures (near gas heaters or open flame), that may result in hydrofluoric acid, hydrochloric acid and phosgene (a fatal nerve gas).

R-12 refrigerant can damage the environment because it is a Chlorofluorocarbon (CFC), which has been proven to add to ozone layer depletion, leading to increasing levels of UV radiation. UV radiation has been linked with an increase in skin cancer, suppression of the human immune system, an increase in cataracts, damage to crops, damage to aquatic organisms, an increase in ground-level ozone, and increased global warming.

R-134a refrigerant is a greenhouse gas which, if allowed to vent into the atmosphere, will contribute to global warming (the Greenhouse Effect).

It is usually more economically feasible to have a certified MVAC automotive technician perform A/C system service on your vehicle. Some possible reasons for this are as follows:

  • While it is illegal to service an A/C system without the proper equipment, the home mechanic would have to purchase an expensive refrigerant recovery/recycling machine to service his/her own vehicle.
  • Since only a certified person may purchase refrigerant-according to the Clean Air Act, there are specific restrictions on selling or distributing A/C system refrigerant-it is legally impossible (unless certified) for the home mechanic to service his/her own vehicle. Venting refrigerant in an illegal fashion exposes one to the risk of paying a $25,000 fine to the EPA.

R-12 Refrigerant conversion
See Figure 6

If your vehicle still uses R-12 refrigerant, one way to save A/C system costs down the road is to investigate the possibility of having your system converted to R-134a. The older R-12 systems can be easily converted to R-134a refrigerant by a certified automotive technician by installing a few new components and changing the system oil.

The cost of R-12 is steadily rising and will continue to increase, because it is no longer imported or manufactured in the United States. Therefore, it is often possible to have an R-12 system converted to R-134a and recharged for less than it would cost to just charge the system with R-12.

If you are interested in having your system converted, contact local automotive service stations for more details and information.

Figure 6 R-134a and R-12 refrigerants can not be combined together.
R-134a and R-12 refrigerants can not be combined together.

Air conditioning maintenance
See Figure 7, 8, 9 and 10

Although the A/C system should not be serviced by the do-it-yourselfer, preventive maintenance can be practiced to help maintain the efficiency of the vehicle's A/C system. For preventive maintenance, perform the following:

  • The easiest and most important preventive maintenance for your A/C system is to be sure that it is used on a regular basis. Running the system for five minutes once a month (no matter what the season) will help ensure that the seals and all internal components remain lubricated.

Some newer vehicles automatically operate the A/C system compressor whenever the windshield defroster is activated. When running, the compressor lubricates the A/C system components; therefore, the A/C system would not need to be operated each month.

  • In order to prevent heater core freeze-up during A/C operation, it is necessary to maintain proper antifreeze protection. Use a hand-held coolant tester (hydrometer) to periodically check the condition of the antifreeze in your engine's cooling system.

Antifreeze should not be used longer than the manufacturer specifies.

  • For efficient operation of an air conditioned vehicle's cooling system, the radiator cap should have a holding pressure that meets manufacturer's specifications. A cap that fails to hold these pressures should be replaced.
  • Any obstruction of or damage to the condenser configuration will restrict airflow that is essential to its efficient operation. It is, therefore, a good rule to keep this unit clean and in proper physical shape.

Bug screens that are mounted in front of the condenser (unless they are original equipment) are regarded as obstructions.

  • The condensation drain tube expels any water that accumulates on the bottom of the evaporator housing into the engine compartment. If this tube is obstructed, the air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle's floor.

Figure 7A coolant tester can be used to determine the freezing and boiling levels of the coolant in your vehicle.
A coolant tester can be used to determine the freezing and boiling levels of the coolant in your vehicle.

Figure 8 View of a common compressor and service fittings.
View of a common compressor and service fittings.

Figure 9 To ensure efficient cooling system operation, inspect the radiator cap gasket and seal.
To ensure efficient cooling system operation, inspect the radiator cap gasket and seal.

Figure 10 On vehicles so equipped, don't forget to check the rear A/C vents for dirt or debris.
On vehicles so equipped, don't forget to check the rear A/C vents for dirt of debris.

System inspection

Although the A/C system should not be serviced by the do-it-yourselfer, A/C system inspections can be performed to help maintain the efficiency of the vehicle's A/C system. For A/C system inspection, perform the following:

The easiest and often most important check for the air conditioning system consists of a visual inspection of the system components. Visually inspect the air conditioning system for refrigerant leaks, damaged compressor clutch, abnormal compressor drive belt tension and/or condition, plugged evaporator drain tube, blocked condenser fins, disconnected or broken wires, blown fuses, corroded connections and poor insulation.

Checking for oil leaks
See Figure 11

Refrigerant leaks show up as oily areas on the various components because the compressor oil is transported around the entire system along with the refrigerant. Look for oily spots on all the hoses and lines, and especially on the hose and tubing connections. If there are oily deposits, the system may have a leak, and you should have it checked by a certified air conditioning specialist.

Figure 11 Run your hand along the underside of all hose connections and check for leaks. If you find a leak, have it fixed by a certified air conditioning specialist.
Run your hand along the underside of all hose connections and check for leaks.

Keeping the condenser clear
See Figures 12 and 13

Periodically inspect the front of the condenser for bent fins or foreign material (dirt, bugs, leaves, etc.). If any cooling fins are bent, straighten them carefully. You can remove any debris with a stiff bristle brush.

Figure 12 The position of the condenser in front of the radiator makes it particularly susceptible to collecting debris. Periodically, remove the accumulated bugs, leaves and other trash from the condenser.
The position of the condenser in front of the radiator makes it particularly susceptible to collecting debris.

Figure 13 On models with rear A/C, make sure to clean and inspect the rear condenser also.
On models with rear A/C, make sure to clean and inspect the rear condenser also.

Checking the compressor belt

For belt inspection, adjustment and replacement please refer to the section on the Cooling system.

Checking the refrigerant level

There are two ways to check refrigerant level. On vehicles equipped with sight glasses, checking the refrigerant level is a simple matter. Many late model vehicles, however, do not have a sight glass, and you have to check the temperature of the lines to determine the refrigerant level.

With sight glass
See Figures 14 and 15

The sight glass is normally located in the head of the receiver/drier. The receiver/drier is not hard to locate. It's a large metal cylinder that looks something like a fire extinguisher. Sometimes the sight glass is located in one of the metal lines leading from the top of the receiver/drier. Once you've found it, wipe it clean and proceed as follows:

  1. With the engine and the air conditioning system running, look for the flow of refrigerant through the sight glass. If the air conditioner is working properly, you'll be able to see a continuous flow of clear refrigerant through the sight glass, with perhaps an occasional bubble at very high temperatures.
  2. Cycle the air conditioner on and off to make sure what you are seeing is clear refrigerant. Since the refrigerant is clear, it is possible to mistake a completely discharged system for one that is fully charged. Turn the system off and watch the sight glass. If there is refrigerant in the system, you'll see bubbles during the off cycle. If you observe no bubbles when the system is running, and the airflow from the unit in the vehicle is delivering cold air, everything is OK.
  3. If you observe bubbles in the sight glass while the system is operating, the system is low on refrigerant. Have it checked by a professional.
  4. Oil streaks in the sight glass are an indication of trouble. Most of the time, if you see oil in the sight glass, it will appear as a series of streaks, although occasionally it may be a solid stream of oil. In either case, it means that part of the charge has been lost.

Figure 14 Oils streaks (A), constant bubbles (B) or foam (C) indicate there is not enough refrigerant in the system. Occasional bubbles during the initial operation are normal. A clear sight glass indicates a proper charge of refrigerant or no refrigerant at all, which can be determined by the presence of cold air at the outlets in the vehicle. If the glass is clouded with a milky white substance, have the receiver/dryer checked by a certified air conditioning specialist.
Oils streaks, constant bubbles or foam indicate there is not enough refrigerant in the system.

Figure 15 Look through the sight glass for refrigerant flow.
Look through the sight glass for refrigerant flow.

Without sight glass
See Figure 16

On vehicles that are not equipped with sight glasses, it is necessary to feel the temperature difference in the inlet and outlet lines at the receiver/drier to gauge the refrigerant level. Use the following procedure:

  1. Locate the receiver/drier. It will generally be up front near the condenser. It is shaped like a small fire extinguisher and will always have two lines connected to it. One line goes to the expansion valve and the other goes to the condenser.
  2. With the engine and the air conditioner running, hold a line in each hand and gauge their relative temperatures. If they are the same approximate temperatures, the system is correctly charged.
  3. If the line from the expansion valve to the receiver/drier is a lot colder than the line from the receiver/drier to the condenser, then the system is overcharged. It should be noted that this is an extremely rare condition.
  4. If the line that leads from the receiver/drier to the condenser is a lot colder than the other line, the system is undercharged.
  5. If the system is undercharged or overcharged, have it checked by a professional air conditioning mechanic.

Figure 16 Checking the refrigerant charge if the system has no sight glass.
Checking the refrigerant charge if the system has no sight glass.

Operate the air conditioner periodically

Many problems can be avoided by simply running the air conditioner at least once a week, regardless of the season. Simply let the system run for at least five minutes a week (even in the winter), and you'll keep the internal parts lubricated as well as prevent the hoses from hardening.

Air conditioning system maintenance intervals

Location guide (thumbnail)
1. Check/adjust drive belt Every 1000 miles or 1 month
2. Check/clean condenser Every 3000 miles or 3 months
3. Check for refrigerant leaks Every 3000 miles or 3 months
4. Check refrigerant level Every 3000 miles or 3 months
5. Operate compressor Once a week for a few minutes
(regardless of season)

Troubleshooting air conditioning problems

Return to page 1 of Air conditioning

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©1998 W. G. Nichols - Chilton's Easy Car Care