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Component Tests - Climate Control System Refrigerant System Performance Evaluation CAUTION: Only equipment designed for R-134a refrigerant systems can be used for refrigerant system diagnosis. R- 12 refrigerant service equipment should never be substituted or damage to the system or equipment may result.

The best way to diagnose a condition in the refrigerant system is to note the system pressures (shown by the manifold gauges) and the clutch cycle rate and times. Then, compare the findings to the charts.

- The system pressures are low (A/C compressor suction) and high (A/C compressor discharge).
- An A/C clutch cycle is the time (in seconds) the A/C clutch is engaged plus the time it is disengaged (time on plus time off).
- A/C clutch cycle rate is the number of cycles per minute (60 seconds/A/C clutch cycle time).

The following procedure is recommended for achieving accurate diagnosis results in the least amount of time.

1. Before starting the diagnosis procedures, perform the following vehicle setup procedures.

- Park vehicle indoors or in the shade.
- Close all of the vehicle doors.
- Close all of the vehicle windows.

2. Connect a R-134a Gauge Manifold and Hose Set 176-R032A, or equivalent meeting Ford specification, to the system. Purge air from the red and blue hoses by loosening the fittings at the gauge set. Open only long enough for air to escape and then tighten the fittings.
NOTE: The test conditions, specified at the top of each chart, must be met to obtain accurate test results.
3. Start the engine and turn on the A / C system to maximum (recirculation air) and heater blower motor on maximum. Run engine at 1500 rpm for 10 minutes.
4. As soon as the system is stabilized, record the high and low pressures as shown by the manifold gauges. The low side should cycle between approximately 169 and 276-324 kPa (24.5 and 40-47 psi). As low pressure drops, high pressure should rise. When the A/C clutch disengages, the low side should rise and the high side should drop.
5. Determine the A / C clutch cycle rate per minute (A/C clutch on time plus off time is a cycle).
6. Record the A/C clutch oft time in seconds.
7. Record the A/C clutch on time in seconds.
8. Record the center A/C register discharge temperature.
9. Determine and record the ambient temperature.
10. Compare test readings with the applicable chart.

NOTE: The charts on the following pages are applicable to vehicles with front A / C only. Refer to Technical Service Bulletins (TSBs) for auxiliary climate control system charts.

- Plot a vertical line for recorded ambient temperature from the scale at the bottom of each chart to the top of each chart.
- Plot a horizontal line for each of the other test readings from the scale at the LH side of the appropriate chart.