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11) Check inlet port temperature-to-outlet port temperature relationship using the graph. For example, if temperature
near air inlet of HVAC unit is 30 °C (86 °F) and the one at air outlet of center ventilation louver is 17 °C (62.6 °F),
their crossing point is within acceptable range as shown in the graph. In this case, cooling performance is
satisfactory and proper.
12) If crossing point is out of acceptable range, diagnose trouble referring to the following table.
[A]: Temp at air outlet of center ventilation louver
[B]: Temp near air inlet of HVAC unit
Thermometer at center duct
Condition
Crossing point is higher
than acceptable range
("E" area)
Crossing point is lower
than acceptable range
("F" area)
NOTE
If ambient temperature is approximately 30 °C (86 °F), it is possible to diagnose A/C system in detail
referring to the following table.
F
C
82.4
28
80.6
27
78.8
26
77.0
25
75.2
24
73.4
23
71.6
22
69.8
21
68.0
20
[A]
66.2
19
64.4
18
62.6
17
60.8
16
59.0
15
57.2
14
55.4
13
53.6
12
51.8
11
50.0
10
48.2
9
46.4
8
25
77
Possible cause
Insufficient or excessive charge of refrigerant
Dirty or bent A/C evaporator fins
Air leakage from cooling (heater) unit or air duct
Malfunctioning, switch over function of door in
cooling (heater) unit
Compressor malfunction
Insufficient air volume from center duct
(Heater blower malfunction)
Compressor malfunction
Air Conditioning System: Manual Type 7B-13
%
70
"E"
[C]
[D]
30
"F"
30
35
C
86
95
F
[B]
I7RS0A721007-01
[C]: Humidity
[D]: Acceptable range
Check refrigerant pressure.
Clean or repair.
Repair or replace.
Repair or replace.
Check compressor.
Check blower motor and fan.
Check compressor.
Correction
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