Air Conditioning System: Manual Type 7B-13
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.
Thermometer at center duct
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.
[A]: Temp at air outlet of center ventilation louver [C]: Humidity
[B]: Temp near air inlet of HVAC unit [D]: Acceptable range
Condition Possible cause Correction
Crossing point is higher
than acceptable range
(“E” area)
Insufficient or excessive charge of refrigerant Check refrigerant pressure.
Dirty or bent A/C evaporator fins Clean or repair.
Air leakage from cooling (heater) unit or air duct Repair or replace.
Malfunctioning, switch over function of door in
cooling (heater) unit
Repair or replace.
Compressor malfunction Check compressor.
Crossing point is lower
than acceptable range
(“F” area)
Insufficient air volume from center duct
(Heater blower malfunction)
Check blower motor and fan.
Compressor malfunction Check compressor.
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
46.4
48.2
50.0
51.8
53.6
55.4
57.2
59.0
60.8
62.6
64.4
66.2
68.0
69.8
71.6
73.4
75.2
77.0
78.8
80.6
82.4
25 30 35
77 86 95
F C
C
F
“E”
“F”
30
70
%
[A]
[B]
[C]
[D]
I7RS0A721007-01