R-12 refrigerant is a chlorofluorocarbon which, when released into the atmosphere, contributes to the depletion of the ozone layer in the upper atmosphere. Ozone filters out harmful radiation from the sun. Consult the laws in your area before servicing the air conditioning system. In some states it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician and a recovery/recycling equipment meeting Society of Automotive Engineers (SAE) Standard J 1991 is used.
Because of the importance of the necessary safety precautions that must be exercised when working with air conditioning systems and R-12 refrigerant, a recap of the safety precautions are outlined.
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 fitting or perform any work other than that outlined here.
Checking For Oil Leaks
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, especially on the hose and tubing connections. If there are oily deposits, the system may have a leak, have it checked by a qualified repairman.
A small area of oil on the front of the compressor is normal and no cause for alarm.Checking The Compressor Belt
Refer to the Drive Belt section in this section.Keep The Condenser Clear
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 with needlenose pliers. You can remove any debris with a stiff bristle brush or hose.Operate The Air Conditioning System Periodically
A lot of air conditioning 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 a least 5 minutes a week (even in the winter) and you'll keep the internal parts lubricated as well as preventing the hoses from hardening.Leak Testing the System
See Figure 1
There are several methods of detecting leaks in an air conditioning system; among them, the two most popular are (1) halide leak detection or the open flame method and (2) electronic leak detector.
The Halide Leak Detection tool No. J-6084 or equivalent, is a torch like device which produces a yellow-green color when refrigerant is introduced into the flame at the burner. A purple or violet color indicates the presence of large amounts of refrigerant at the burner.
An Autobalance Refrigerant Leak Detector tool No. J-29547 or equivalent, is a small portable electronic device with an extended probe. With the unit activated, the probe is passed along those components of the system which contain refrigerant. If a leak is detected, the unit will sound an alarm signal or activate a display signal depending on the manufacturer's instructions as the design and function of the detection may vary significantly.
See Figure 2
Most of the service work performed in air conditioning requires the use of a set of two gauges, one for the high (head) pressure side of the system, the other for the low (suction) side.
The low side gauge records both pressure and vacuum. Vacuum readings are calibrated from 0-30 in. Hg and the pressure graduations read from 0-60 psi.
The high side gauge measures pressure from 0-600 psi.
Both gauges are threaded into a manifold that contains two hand shut-off valves. Proper manipulation of these valves and the use of the attached test hoses allow the user to perform the following services:
- Test high and low side pressures.
- Remove air, moisture and/or contaminated refrigerant.
The manifold valves are designed so they have no direct effect on the gauge readings but serve only to provide for or cut off the flow of refrigerant through the manifold. During all testing and hook-up operations, the valves are kept in a Closed position to avoid disturbing the refrigeration system.Service Valves
See Figure 3
For the user to diagnose an air conditioning system, he or she must gain entrance to the system in order to observe the pressures; the type of terminal for this purpose is the Schrader valve.
The Schrader valve is similar to a tire valve stem and the process of connecting the test hoses is the same as threading a hand pump outlet hose to a bicycle tire. As the test hose is threaded to the service port the valve core is depressed, allowing the refrigerant to enter the test hose outlet. Removal of the test hose automatically closes the system.
Extreme caution must be observed when removing the test hoses from the Schrader valves as some refrigerant will normally escape, usually under high pressure; observe safety precautions.Using the Manifold Gauges
The following are step-by-step procedures to guide the user to the correct gauge usage.
- Remove the caps from the high and low side service ports. Make sure both gauge valves are Closed.
- Connect the low side test hose to the service valve that leads to the evaporator (located between the evaporator outlet and the compressor).
- Attach the high side test hose to the service valve that leads to the condenser.
- Mid-position the hand shutoff type service valves.
- Start the engine allow it to warm-up. All testing of the system should be done after the engine and system has reached normal operating temperatures (except when using certain charging stations).
- Adjust the air conditioner controls to Max. Cold.
Observe the gauge readings. When the gauges are not being used it is a good idea to:
- Keep both hand valves in the Closed position.
- Attach both ends of the high and low service hoses to the manifold, if extra outlets are present on the manifold or plug them (if not).
DISCHARGING THE SYSTEM
Discharging the refrigerant from the air conditioning system should be performed by a qualified facility equipped with recovery/recycling equipment meeting Society of Automotive Engineers (SAE) Standard J 1991.
EVACUATING THE SYSTEM
Before charging any system it is necessary to purge the refrigerant and draw out the trapped moisture with a suitable vacuum pump. Failure to do so will result in ineffective charging and possible damage to the system.
- Connect both service gauge hoses to the high and low service outlets. Connect a recovery/recharging station to the system as outlined in the information supplied with the unit in use.
- Discharge the air conditioning system using the a recovery/recycling station. Do not allow the refrigerant to discharge into the atmosphere.
- Install the center charging hose of the gauge set to the vacuum pump.
- Operate the vacuum pump for at least one hour. If the system has been subjected to open conditions for a prolonged period of time, it may be necessary to pump the system down overnight. Refer to the System Sweep procedure.
If the low pressure gauge does not show at least 28 in. Hg within 5 minutes, check the system for a leak or loose gauge connectors.
- Close the hand valves on the gauge manifold.
- Turn Off the pump.
- Observe the low pressure gauge to determine if the vacuum is holding. A vacuum drop may indicate a leak.
An efficient vacuum pump can remove all the air contained in a contaminated air conditioning system very quickly, because of its vapor state. Moisture, however, is far more difficult to remove because the vacuum must force the liquid to evaporate before it will be able to be removed from the system. If the system has become severely contaminated, as it might become after all the charge was lost in conjunction with vehicle accident damage, moisture removal is extremely time consuming. A vacuum pump could remove all of the moisture only if it were operated for 12 hours or more.
Under these conditions, sweeping the system with refrigerant will speed the process of moisture removal considerably. To sweep, follow the following procedure:
- Connect the vacuum pump to the gauges, operate it until the vacuum ceases to increase, then, continue the operation for ten or more minutes.
- Charge the system with 50% of its rated refrigerant capacity.
- Operate the system at fast idle for 10 minutes.
- Discharge the system using a recovery/recycling station.
- Repeat (twice) the process of charging to 50% capacity, running the system for ten minutes, then, discharge it for a total of three sweeps.
- Replace the drier.
- Pump the system down as in Step 1.
- Charge the system.
Charging the air conditioning system should be performed by a qualified facility equipped with recovery/recycling equipment meeting Society of Automotive Engineers (SAE) Standard J 1991.
- Start the engine, operate it with the choke Open and normal idle speed, then, position the air conditioning control lever Off.
- Allow about 1 lb. of refrigerant to enter the system through the low side service fitting on the accumulator.
- After the 1 lb. of refrigerant enters the system, position the control lever to Normal (the compressor will engage) and the blower motor on Hi speed; this operation will draw the remainder of the refrigerant into the system.
To speed up the operation, position a fan in front of the condenser; the lowering of the condenser temperature will allow refrigerant to enter the system faster.
- When the system is charged, turn Off the refrigerant source and allow the engine to run for 30 seconds to clear the lines and gauges.
- With the engine running, remove the hose adapter from the accumulator service fitting (unscrew the hose quickly to prevent refrigerant from escaping).
- Replace the accumulator protective caps and turn the engine Off.
- Using a leak detector, inspect the air conditioning system for leaks. If a leak is present, repair it.