Refrigerant System Performance

iThe best way to diagnose a concern in the refrigerant system is to note the system pressures (shown by the manifold gauges) and the clutch cycle rate and times.

The following procedure is recommended for achieving accurate diagnosis results in the least amount of time.
1. Connect a manifold gauge set, from a Rotunda Air Conditioning Service Kit 063-00010 or equivalent, to system. Purge air from red and blue hoses using system pressure by loosening fittings at gauge set. Open only long enough for air to escape and then tighten fittings.

NOTE: IMPORTANT TEST REQUIREMENTS:
The following test conditions must be established to obtain accurate clutch cycle rate and cycle time readings:
^ Run engine at 1500 rpm for 10 minutes.
^ Operate A/C System on max A/C (recirculating air).
^ Run blower at max speed.
^ Stabilize in car temperature 70°F. to 80°F. (21°C. to 22°C.).

2. Start engine. Turn on A/C system.
3. As soon as system is stabilized, record high and low pressures as shown by manifold gauges. The low side should cycle between approximately 25 and 45 psi. As low pressure drops, high pressure should rise. When the clutch disengages, the low side should rise and the high side should drop.
4. Determine clutch cycle rate per minute (clutch on time plus off time is a cycle).
5. Record clutch OFF time in seconds.
6. Record clutch ON time in seconds.
7. Record center register discharge temperature.
8. Determine and record ambient temperatures.
9. Compare test readings with the charts in the illustrations.
^ From bottom scale of chart to top of chart, plot a vertical line for recorded ambient temperature.
^ Plot a horizontal line for each of the other test readings beginning at LH scale of appropriate chart.

Normal Center Register Discharge Temperatures:

Normal Fixed Orifice Tube Cycling Clutch Refrigerant System Pressures:

Total Clutch Cycle Time - Seconds:

Normal Clutch Off Time - Seconds:

Normal Clutch Cycle Rate Per Minute:

Normal Clutch On Time - Seconds: