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 attempting to service the air conditioning system. In some states it is illegal to perform repairs involving refrigerant unless the work is done by a certified technician.
Visually inspect the air conditioning system for refrigerant leaks, damaged compressor clutch, compressor drive belt tension and condition, plugged evaporator drain tube, blocked condenser fins, disconnected or broken wires, blown fuses, corroded connections and poor insulation.
A refrigerant leak will usually appear as an oily residue at the leakage point in the system. The oily residue soon picks up dust or dirt particles from the surrounding air and appears greasy. Through time, this will build up and appear to be a heavy dirt impregnated grease. Most leaks are caused by damaged or missing O-ring seals at the component connections, damaged charging valve cores or missing service gauge port caps.
The evaporator drain tube expels the condensation that accumulates on the bottom of the evaporator housing, into the engine compartment. If the tube is obstructed, air conditioning performance can be restricted and condensation buildup can spill over onto the vehicle floor.
Any obstruction of or damage to the condenser configuration will restrict the air flow which is essential to its efficient operation. It is therefore a good rule to keep the condenser clean and in proper physical shape.
Move the refrigerant hoses and look for signs of cracks, rotted hoses or loose connections.
SYSTEM PERFORMANCE CHECK
See Figures 1, 2 and 3
- Connect a manifold gauge set to the air conditioning system as explained in this section.
- Start the engine and turn the air conditioner ON .
- As soon as the system is stabilized, record the high and low pressures shown on the manifold gauges. The low side should cycle between approximately 25-45 psi (15-310 kPa). As low pressure drops, high pressure should rise. When the compressor clutch is disengaged, the low side should rise and the high side should drop.
- Determine the clutch cycle rate per minute. Clutch on time + clutch off time = 1 cycle.
When the ambient temperature is above 80ºF (26ºC), the clutch may not cycle.
Record the following:
Clutch OFF time in seconds
- Plot a vertical line for recorded ambient temperature from the scale at the bottom of each chart to the top of each chart in the figures.
- Plot a horizontal line for each of the other test readings from the scale at the left-hand side of the appropriate chart.
- If the point where the 2 lines cross on each of the charts falls within the dark band, the system is operating properly. If the lines cross outside the dark band on one or more of the charts, there is a malfunction. To determine the cause of the malfunction, refer to the chart in the figure.
See Figures 4 and 5
Most of the service work performed in air conditioning requires the use of a set of two gauges, one for the high pressure side of the system and the other for the low pressure side of the system.
The low side gauge records both pressure and vacuum. Vacuum readings are calibrated from 0 to 30 inches Hg (0-99 kPa) and the pressure graduations read from 0 to no less than 60 psi (0-414 kPa). The high side gauge measures pressure from 0 to at least 600 psi (4140 kPa).
Both gauges are threaded into a manifold that contains two hand shut-off valves. The manifold valves are designed so they have no direct effect on gauge readings, but serve only to meter the flow of refrigerant through the manifold. During all testing and hook-up operations, the valves are kept in the closed position to avoid disturbing the refrigeration system.
Connect the manifold gauge set as follows:
- Turn both manifold valves fully to the right, to close the high and low pressure hoses to the center manifold and hose.
- Remove the caps from the high and low pressure service gauge port valves. The high pressure service gauge port valve is located between the compressor and the condenser on the high pressure discharge line. The low pressure service gauge port valve is located between the suction accumulator/drier and the compressor on the low pressure suction line, or is located directly on the suction accumulator/drier.
- Connect the high and low pressure hoses to the respective high and low pressure service gauge port valves.
If the manifold gauge set hoses do not have valve depressing pins in them, install fitting adapters T4P-1933-S/R or equivalent on the low and high pressure hoses. High side adapter set D81L-1933-A or Motorcraft® tool YT-354/355 or equivalent, must be used to connect the manifold gauge set to the high pressure service gauge port valve.
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 standards.
- Connect a manifold gauge set as explained in this section.
- Leak test the system, as explained in this section.
- Properly discharge the refrigerant from the system into a recovery/recycling machine.
- Make sure both manifold gauge valves are closed (turned all the way to the right).
- Make sure the center hose connection at the manifold gauge set is tight. Connect the center hose to a suitable vacuum pump.
- Open the manifold gauge set valves and start the vacuum pump.
- Run the vacuum pump until the low pressure gauge reads at least 25 in. Hg (82.5 kPa) or as close to 30 in. Hg (99 kPa) as possible. Continue to operate the vacuum pump for 15 minutes. If a part of the system has been replaced, operate the vacuum pump for 20-30 minutes.
- When evacuation is completed, close the manifold gauge set valves and turn the vacuum pump off.
- Observe the low pressure gauge for 5 minutes to make sure vacuum is held. If vacuum is held, the system can be charged. If vacuum is not held for 5 minutes, the system might have a leak. Repair the leak and evacuate the system again.
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.
- Evacuate The A/C system.
- Make sure the manifold gauge set valves are still closed to the center hose, then disconnect the vacuum pump.
- Connect the center hose to a refrigerant charging container.
- Loosen the center hose at the manifold gauge set and open the refrigerant charging cylinder valve. Allow only enough refrigerant to escape to purge the air and moisture from the center hose, then tighten the center hose connection at the manifold gauge set.
- Disconnect the wire harness connector from the clutch cycling pressure switch and install a jumper wire across the 2 terminals of the connector.
- Open the manifold gauge set low side valve to let refrigerant enter the system. Keep the refrigerant container in an upright position if the vehicle's low pressure service gauge port is not on the suction accumulator/drier.
- When no more refrigerant is being drawn into the system, start the engine and move the control panel lever to the AC position and the blower switch to HI to draw the remaining refrigerant into the system.
- Continue adding refrigerant to the system until the required weight of refrigerant is in the system.
- Close the manifold gauge set low pressure valve and the refrigerant supply valve.
- Remove the jumper wire from the clutch cycling pressure switch connector and engage the connector to the pressure switch.
- Operate the system until pressures stabilize to verify normal operation and system pressures.
- In high ambient temperatures, it may be necessary to operate a high volume fan positioned to blow air through the radiator and condenser to aid in cooling the engine and prevent excessive refrigerant system pressures.
- When charging is completed and system operating pressures are normal, disconnect the manifold gauge set from the vehicle. Install the protective caps on the service gauge port valves.
See Figure 6
This procedure requires the use of electronic leak detector tool 055-00014, 055-00015 or equivalent.
Turn the control switch on the electronic leak detector to the ON position. The detector will automatically calibrate itself. Move the detector probe at approximately 1 in. per second in the suspected leak area. When escaping refrigerant gas is located, the ticking/beeping signal from the detector will increase in ticks/beeps per second. If the gas is relatively concentrated, the signal will be increasingly shrill. Follow the instructions included with the detector for further operating information.