38
MODGAS-XWR2 Technical Guide
Other Checks
0-3V (SAT OPTIONS Jumper Setting 1) and 0-5V (SAT
OPTIONS Jumper Setting 2) Supply Air Temperature
Sensor
If you suspect the Supply Air Temperature Sensor is not reading
correctly, make sure the wiring terminal connections are tight and
that any wiring splices are properly connected. You can check the
operation of the Supply Air Temperature Sensor by measuring
the resistance or voltage using a digital multimeter. Set the meter
to DC Volts. Place the positive probe on the AI terminal and the
negative probe on the GND terminal. Read the DC Volts and
find that voltage in
Tables 7 and 8, this page and on page 39
.
Read the temperature corresponding with that voltage and
determine the actual temperature the sensor is exposed to. If
the temperature from the chart is different by more than a few
degrees, the sensor is likely defective or damaged.
You can also check the sensor resistance to determine correct
operation. To read the resistance, set the meter to ohms. Unplug
the sensor connector from the board and measure the resistance
across the disconnected wires. This resistance should match the
corresponding temperature from
Tables 7 and 8, this page and
on page 39
.
Thermistor Sensor Testing Instructions
1. Use the resistance column to check the thermistor
sensor while disconnected from the controllers (not
powered).
2. Use the voltage column to check sensors while
connected to powered controllers. Read voltage with
meter set on DC volts. Place the “-” (minus) lead on
GND terminal and the “+” (plus) lead on the sensor
input terminal being investigated.
Table 7: 0-3V Temperature Sensor - Voltage and Resistance for Type III Sensors
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
-10
-23.3
93333
2.98
-5
-20.6
80531
2.94
0
-17.8
69822
2.89
5
-15
60552
2.83
10
-12.2
52500
2.77
15
-9.4
45902
2.71
20
-6.6
40147
2.64
25
-3.9
35165
2.57
30
-1.1
30805
2.49
35
1.7
27140
2.41
40
4.4
23874
2.33
45
7.2
21094
2.24
50
10
18655
2.15
52
11.1
17799
2.11
54
12.2
16956
2.08
56
13.3
16164
2.04
58
14.4
15385
2.00
60
15.6
14681
1.96
62
16.7
14014
1.93
64
17.8
13382
1.89
66
18.9
12758
1.85
68
20
12191
1.81
69
20.6
11906
1.79
70
21.1
11652
1.78
71
21.7
11379
1.76
Temp
(°F)
Temp
(°C)
Resistance
(Ohms)
Voltage @
Input (VDC)
72
22.2
11136
1.74
73
22.8
10878
1.72
74
23.3
10625
1.70
75
23.9
10398
1.68
76
24.4
10158
1.66
78
25.6
9711
1.63
80
26.7
9302
1.59
82
27.8
8893
1.55
84
28.9
8514
1.52
86
30
8153
1.48
88
31.1
7805
1.45
90
32.2
7472
1.41
95
35
6716
1.33
100
37.8
6047
1.24
105
40.6
5453
1.16
110
43.3
4923
1.09
115
46.1
4449
1.02
120
48.9
4030
.95
125
51.7
3656
.88
130
54.4
3317
.82
135
57.2
3015
.76
140
60
2743
.71
145
62.7
2502
.66
150
65.6
2288
.61
Temperature to Resistance/Voltage Chart
Note:
If the voltage is above 3.3 VDC the sensor or wiring is “open.” If the voltage is less than 0.05 VDC, the sensor or wiring is shorted.
TROUBLESHOOTING
SAT Sensor Testing
