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SYSTEM PERFORMANCE TEST
This test is performed to establish the condition of all
components in the system. Observe these conditions
during testing:
1. Place a fan in front of the condenser to simulate
normal ram air flow and allow the system to sta-
bilize.
2. Install a thermometer into the air conditioning
vent closest to the evaporator.
3. Start the engine and operate at 1000 rpm.
4. Evaluate the readings obtained from the
gauges to see if they match the readings for the
ambient temperature.
5. Set air conditioning system at maximum cooling
and maximum blower speed operation.
6. Close all windows and doors to the cab.
7. Carefully feel the hoses and components on the
high side. All should be warm-hot to the touch.
Check the inlet and outlet of receiver-drier for
even temperatures, if outlet is cooler than inlet,
a restriction is indicated.
Use extreme caution when placing hands on high
side components and hoses. Under most normal
conditions these items can be extremely hot.
Ambient Air Temperature
21° C (70° F)
27° C (80° F)
32° C (90° F)
38° C (100° F)
43° C (110° F)
NOTE: All pressures in this chart are for reference, only. Weight is the only absolute means of determining
proper refrigerant charge.
N04031 10/06
TABLE 1. NOMINAL R-134a PRESSURE RANGES
High Side Pressure
820 - 1300 kPa (120 - 190 psi)
950 - 1450 kPa (140 - 210 psi)
1175 - 1650 kPa (170 - 240 psi)
1300 - 1850 kPa (190 - 270 psi)
1450 - 2075 kPa (210 - 300 psi)
Operator Comfort
8. Feel the hoses and components on the low
side. They should be cool to the touch. Check
connections near the expansion valve; the inlet
side should be warm and the outlet side cold.
9. After a minimum of 10 minutes has elapsed and
the system has stabilized, observe the gauge
readings. Compare the readings to the specifi-
cations in Table 1.
NOTE: Pressures may be slightly higher in very
humid conditions and lower in very dry conditions.
Pressures listed in the table are during compressor
clutch engagement.
10. Check the cab vents for cool air. Outlet air tem-
perature should be approximately 16 - 22° C
(30 - 40° F) below ambient air temperature.
11. If pressures and temperatures are not within the
specified ranges, the system is not operating
properly. Refer to Preliminary Checks near the
end of this chapter for tips on diagnosing poor
system performance.
Low Side Pressure
70 - 138 kPa (10 - 20 psi)
70 - 173 kPa (10 - 25 psi)
105 - 210 kPa (15 - 30 psi)
105 - 210 kPa (15 - 30 psi)
105 - 210 kPa (15 - 30 psi)
N4-19
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