Chapter 15 Refrigeration System Diagnosis and Leak Detection 235
Figure 15-9. After the ambient temperatures and system pressures have been determined, the technician can refer to a chart
showing the relationship of pressures and temperatures of a given refrigerant. He or she can use the chart to determine whether the
system has a problem. (General Motors)
Relative
Humidity
(%)
Maximum
Low Side
Pressure
PSIG kPaG
Maximum
High Side
Pressure
PSIG kPaG
Engine
Speed
(rpm)
Maximum Right
Center Air
Outlet
Temperature
°F ° °C °
Ambient
Air Temp
°F ° °C °
20
30
40
50
60
70
80
90
70 21
80 27
90 32
100 38
70 21
80 27
90 32
100 38
70 21
80 27
90 32
100 38
70 21
80 27
90 32
100 38
70 21
80 27
90 32
70 21
80 27
90 32
70 21
80 27
70 21
80 27
90 32
100 38
46 8
47 8
53 12
54 12
2000
2000
2000
2000
2000
2000
2000
2000 48 9
50 10
57 14
60 16
49 9
53 12
60 16
66 19
51 11
56 13
63 17
72 22
53 12
59 15
66 19
78 26
55 13
62 17
70 21
56 13
65 18
73 23
58 14
68 20
37 255
37 255
37 255
38 262
225 1551
275 1896
325 2241
325 2241
240 1655
285 1965
340 2344
360 2482
37 255
37 255
39 269
43 296
37 255
37 255
42 290
49 338
37 255
39 269
46 317
55 379
37 255
42 290
49 338
60 414
37 255
45 310
53 365
41 283
48 331
57 393
45 310
52 359
260 1793
305 2103
355 2448
395 2724
275 1896
320 2206
375 2586
430 2965
290 2000
340 2344
390 2689
445 3068
305 2103
355 2448
405 2792
320 2206
370 2551
420 2896
335 2310
385 2655
Figure 15-10. Gauge readings during normal system operation. The color areas indicate low and
high side pressures, as well as the typical numerical values indicated on the bottom. The normal color
region will be used in other gauge examples in this chapter.
Normal System Operation
Low Side (Suction)
Orifice Tube
Exp. Valve
VDOT
Other
(Varies with ambient temperature) (Varies with ambient temperature)
25-35 psi (172-241 kPa)
15-35 psi (103-241 kPa)
26-32 psi (179-221 kPa)
Sight glass: Clear
150-285 psi (1034-1965 kPa)
150-285 psi (1034-1965 kPa)
150-285 psi (1034-1965 kPa)
Max A/C air temp: 40-50°F (4-10°C)
High Side (Discharge)
0
10
20
30
4
0
50
60
70
80
90
100
110
120
0
50
100
15
0
200
250
3
00
350
400
450
500