There are two particular hazards associated with air conditioning systems and they both relate to the refrigerant gas.
First, the refrigerant gas (R-12) is an extremely cold substance. When exposed to air, it will instantly freeze any surface it comes in contact with, including your eyes. The other hazard relates to fire. Although normally non-toxic, the R-12 gas becomes highly poisonous in the presence of an open flame. One good whiff of the vapor formed by burning R-12 can be fatal. Keep all forms of fire (including cigarettes) well clear of the air conditioning system.
PREVENTIVE MAINTENANCE CHECKS
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, and especially on the hose and tubing connections. If there are oily deposits, the system may have a leak. Refer to Leak Testing procedures.
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 section on Drive Belts.Keeping the Condenser Clean
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.Operating the A/C 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. Let the system run for at least 5 minutes a week (even in the winter), and you'll keep the internal parts well lubricated as well as preventing the hoses from hardening.
REFRIGERANT LEVEL CHECK
There are two ways to check refrigerant level, depending on the model year of your car.
If your car is equipped with an aftermarket (non GM) air conditioner, the following checks may not apply. Contact the manufacturer for instructions on system checks.With Sight Glass (1967 through early 1973)
See Figure 1
The sight glass for checking the refrigerant charge, is located in one of two locations, either on the Receiver Dehydrator (1967-early 73), or on the top of the VIR (valves-in-receiver, late 73-76). The Receiver Dehydrator and the VIR look like small fire extinguishers, the Receiver Dehydrator is located usually on the passenger's side of the radiator, the VIR assembly is located near the fire wall on the passengers side.
This test is most effective if the outside air temperature is 70°F (21°C) or above.
- Place the transmission in Park, and apply the parking brake.
- Have a helper control the accelerator pedal and run the engine to 1500 rpm (fast idle).
- Set the A/C controls on the instrument panel for maximum cold with the blower on HIGH.
- Look at the sight glass on top of the Receiver Dehydrator or VIR. (You'll probably have to wipe it clean first). If a steady stream of bubbles is present in the sight glass, the system is low on charge. There is a good chance the system has a leak.
- If no bubbles are present, the system is either fully charged or completely empty. Feel the high and low pressure lines at the compressor; if no appreciable temperature difference is felt, the system is empty or nearly so.
- If one hose is warm (high pressure) and the other is cold (low pressure), the system may be OK. However, you are probable making these tests because there is something wrong with your air conditioner, so proceed to the next step.
- Have your helper turn the fan control on and off to operate the compressor clutch. Watch the sight glass.
- If bubbles appear when the clutch is disengaged, and disappear when it is engaged, the system is properly charged.
- If the refrigerant takes more than 45 seconds to bubble when the clutch is disengaged, the system is more than likely overcharged. This condition will usually result in poor A/C operation (poor cooling) at low speeds.
- Finally, check for oil streaks in the sight glass, which are a sign 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.
Without Sight Glass (1977 and Later)
The cars built in these years are not equipped with a sight glass in their A/C systems. On these cars it is necessary to feel the temperature difference in the inlet and outlet lines at the VIR to gauge the refrigerant level. Use the following procedure:
- Run the engine until it reaches normal operating temperature.
- Open the hood and all doors to aid in cooling.
- Turn the air conditioner on, move the temperature selector to the first detent to the right of COLD (outside air) and then turn the blower on to HIGH.
- Run the engine at 1000 rpm.
- Feel the temperature of the evaporator inlet and the accumulator outlet with the compressor clutch engaged (see step 7 of the With Sight Glass procedure).
- Both lines should be cold. If the inlet pipe is colder than the outlet pipe, the system is low on charge. Do not attempt to charge the system yourself; take the car to a professional air conditioning mechanic.
DISCHARGING, EVACUATING AND CHARGING THE SYSTEM
The A/C system may be discharged, evacuated or charged using a charging station such as J-23500-01 or a manifold gage set such as J-23575-01 and an approved recovery station. The following guidelines should always be observed:
- Always wear safety goggles and wrap a clean cloth around fittings and connections when doing work that involves opening the refrigeration system.
- Always discharge the air conditioning system at the low side service fitting with a recovery machine attached.
- Perform the entire evacuation and charging procedure through the low-side service fitting.
- Never connect the high-pressure line or other line to the high-side service fitting during discharging or charging the system.
- Before discharging, evacuating or charging the system, the low pressure gage should be calibrated. With the gage disconnected from the refrigerant system, the pointer should indicate the zero mark. Tap the gage several times to assure the pointer is not stuck. If necessary, remove the low pressure gage cover and adjust the pointer to zero with the pointer adjusting screw.
Service Valve Location
The low side service fitting is located on the accumulator or evaporator outlet pipe.
The high side service fitting is located on the high pressure discharge liquid line or muffler.Discharging the System
- With the ignition turned off, remove the cap from the low side service fitting at the accumulator.
- Connect the charging station or the manifold gage set low pressure side gage hose to a approved recovery station. If no discharge occurs, a missing or faulty Schrader valve fitting may be the cause of the problem.
- With the low side of the system discharged, check the high side for any remaining pressure.
- If pressure is found on the high side of the system, discharge the high side using the same procedure as the low side. If pressure is found on the high side of the system, it usually indicates a blockage or restriction and must be corrected before evacuating and charging the system.
- After the system is completely discharged, measure the amount of drained refrigerant oil. If total is 1 / 2 oz. or more, the same amount of 525 viscosity refrigerant oil must be added to the system before evacuating or charging the system. This also includes any amount removed from the system.
Adding oil to the system should take place after the refrigerant system is discharged and before evacuation procedures.
- Remove the refrigeration suction hose at the accumulator outlet pipe connections. Remove and discard the O-ring from suction hose or pipe.
- Pour the correct quantity of new refrigerant oil into the suction hose or pipe.
- Before installing the new O-ring, dip it in 525 viscosity refrigerant oil. Reconnect the suction hose or pipe to the accumulator and tighten connections.
When any CCOT refrigerant components are replaced, new 525 viscosity refrigerant oil must be added as followed:All Compressors:
- If less than 1 oz. is drained - add 2 oz.
- If more than 1 oz. is drained - add same amount.
- Add 3.5 oz. to new accumulator
- Add 3 oz. oil
- Add 1 oz. oil
Evacuating the System Before Charging
If the system has been opened for any repair, or the R-12 charge lost, the system must be evacuated prior to charging.
Evacuation and charging (never vent any gas into the air - while servicing the A/C) is a combined procedure and all gauge lines must be purged with R-12 prior to charging.
There are 3 evacuate and charge procedures.
- J-23500-01 Charging Station (or equivalent) Method
- Disposable Can Method
- Drum Method
Before connecting the vacuum pump to the system, operate the pump connected to the low pressure gauge to determine the vacuum pump capability. If the vacuum system is unable to reach 28-29 in. Hg, the system should be checked for leaks. If no leaks are found, the vacuum pump may require repair.CHARGING STATION METHOD Follow the charging instructions provided with the J-23500-01 charging station or equivalent, noting the following:
- Do not connect the high pressure line to the air conditioning system.
- Keep the high pressure valve on the charging station closed at all times.
- Perform the entire evacuation and charging procedures through the accumulator low-side pressure service fitting.
- Following these procedures will prevent accidental high-side vehicle system pressure being subjected to the charging station in the event a valve sequence error is made while operating the compressor to pull in the refrigerant charge.
If the R-12 drum is used, place it on a scale and note the total weight before charging. Watch the scale during charging to determine the amount of R-12 used.
If disposable 14 oz. R-12 cans are used, close the tapping valve and then attach can(s) following instructions included with the tapping valve or tapping manifold adapter.
Connect manifold gauge set J 23575-01 as follows:
- Low pressure gauge to the accumulator fitting.
- Gauge set center hose to R-12 source.
- High pressure gauge to vacuum pump.
- To begin evacuation of the system with manifold gauge set and vacuum pump connect as follows:
Connect the low side hose to accumulator, center hose to R-12 source and high side hose to vacuum pump, slowly open high-side and low-side gauge valves and begin vacuum pump operation. Pump the system until the low-side gauge reaches 28-29 in. Hg. If this vacuum specification can't be reached, close the vacuum pump control valve and looked for a leak at the connections or the pump.
- When the gauge reaches prescribed vacuum, the system is fully evacuated. Close the high-side gauge set valve and turn off the vacuum pump.
- Watch the low-side gauge to be sure the vacuum holds for 5 minutes. If vacuum is held, disconnect the vacuum hose at the gauge set and proceed to charge the system.
- If the vacuum does not hold for 5 minutes, charge the system with 1 / 2 lb. R-12 and leak check. Discharge the system again and repair the leak as necessary. Repeat evacuation procedure.
Charging the System
- Start the engine. Run until engine operating temperature is reached. Set the A/C mode control lever in OFF position.
- With the R-12 drum or 14 oz. can(s) inverted, open R-12 source valve(s) and allow 1 lb. or one 14 oz. can of liquid R-12 to flow into system through the low-side service fitting.
- As soon as 1 lb. or one 14 oz. can of R-12 has been added to system, immediately engage the compressor by setting the A/C mode lever to NORM and blower speed on HI , to draw in the remainder of the R-12 charge.
The charging operation can be accelerated by using a large volume fan to pass air over the condenser. If the condenser temperature is maintained below the charging cylinder temperature, the R-12 will enter the system more rapidly.
- Turn off the R-12 source valve and run the engine for 30 seconds to clear the lines and gauges.
- With the engine running, remove the charging low-side hose adapter from the accumulator service fitting.
- Replace the protective cap on the accumulator fitting.
- Turn the engine off.
- Leak check system with an electronic leak detector J-29547 or equivalent.
- Start the engine and check the system performance.
LEAK TESTING THE SYSTEM
Liquid Leak Detectors
By applying test solution to the area suspected with a swab that is attached to the bottle cap, bubbles will form within seconds if there is a leak. However, restricted areas, such as the evaporator of condenser will require the use of an electronic leak detector.Electronic Leak Testers
The most accurate tool to locate a leak is the electronic leak tester. The H-10 leak detector J-26934 is a 110-volt, AC powered tester while the refrigerant leak detector J-29547 is a portable, battery operated model. Both models give a visual and/or audible signal when a leak is detected.
The success of both electronic leak testers depends upon carefully following the manufacturer's instructions.
FLUSHING THE SYSTEM
To assure removal of any system contamination (i.e., metal particles) resulting from a damaged or seized compressor, follow the flush procedure outlined below.
R-11 is the only approved solvent for flushing the A/C system. Use extreme caution and adhere to all safety precautions governing the use of refrigerants when flushing the system.
- Discharge the system into an approved recovery station.
- Disconnect all refrigerant line fittings and discard O-rings.
- Remove the orifice tube and discard.
- Close all the valves on the manifold gage set. Connect the gage set to the R-11 container.
- Remove the evaporator core. With flushing tool J-3383 or equivalent, slowly force liquid R-11 into the bottom of core until bubbles and liquid R-11 flows from the top of core. Continue flushing until only liquid R-11 flows from the top of core. Wait 5 minutes then drain the evaporator.
- Remove the condenser and repeat step 5.
- Remove the compressor. Drain the compressor oil through the suction and discharge ports. Fill the compressor with R-11 through the suction port until it runs out of the discharge port. Rotate the compressor clutch 2 or 3 times and drain compressor after 5 minutes. If the compressor will not turn, complete disassembly of the compressor will be necessary.
- Cap one end of the refrigerant lines and fill all lines with R-11. Allow enough R-11 to flow through the lines to thoroughly remove any foreign materials. Wait 5 minutes then drain lines.
- Flush out R-11 thoroughly from all components and lines using R-12.
- Replace the accumulator, orifice tube and all O-rings. If required, install a new compressor. Dip all new O-rings in 525 viscosity refrigerant oil.
Flushing the refrigerant system removes all the refrigerant oil from the system. The total system oil charge is 6 oz. (180 ml). Add 3 oz. to the compressor and 3 oz. to the accumulator.
- Reconnect the flushed refrigerant lines and components, then tighten to the recommended torque specifications.
- Evacuate, charge, leak test and check the refrigerant system performance.
Component temperature must be a minimum of 75°F (24°C) to thoroughly remove R-11 from the system. The use of heat lamps on the compressor, evaporator and condenser is recommended to assist in the proper evacuation of R-11 and will reduce the evacuation time.
REFRIGERATION SYSTEM CHECK
If the A/C system performance test indicates a fault due to abnormal refrigeration system pressures, the following items should be checked:
- Check both the condenser and the radiator for damage fins, blocking the air flow.
- Check for kinks in the evaporator or condenser cores. Also, check for kinks in lines, hoses, tubes and other passages.
- Check for proper A/C belt tension.
- Check for proper air gap between clutch plate and clutch rotor friction surfaces, causing compressor clutch slippage.
- Check the refrigerant system for leaks, blockage or moisture in the system.