IM 613 / Page 26 (Rev. 7/99)
Test Procedures
This section contains troubleshooting procedures for the
following:
• Microprocessor problems
• Power supply problems
• Erroneous temperature readings
• Temperature sensor faults (codes 2, 10, 11, 12, 13, and
14)
• Digital input faults (codes 3, and 5)
• Brownout fault (code 6)
• Actuator feedback faults (codes 7, 8, and 9)
• Master/slave communication error fault (code 16)
Microprocessor Problems
The power and status LED indications can aid in UVC diagnostics.
Power LED: Immediately after power is applied to the UVC, the
watchdog LED should illuminate continuously.
If the LED does not illuminate, check that the UVC power supply
is intact (see “Power Supply Problems” below).
Status LED: Approximately 40 seconds after power is applied
to the UVC, the status LED should illuminate as shown in Table
1. If the LED fails to respond properly, either there is a software
problem or the UVC is defective. If a PC and the proper software
is available, try downloading new software. If this does not help,
the UVC is defective and must be replaced.
Power Supply Problems
The UVC requires a 24 VAC power supply. It is connected to
the board at the section labeled “POWER” (terminal 6,24V). A
transformer steps down the line voltage to the required 24 VAC:
transformer X2 or X3 (line to 24 VAC). (Transformer X2 is used
only on units with compressors.) Refer to the unit wiring diagram.
If a problem with the UVC power supply is suspected, check the
following:
1. Verify that the main power switch is at “On.”
2. Check the voltage at the secondary of transformer X2 or
X3. It should be approximately 24 VAC (load dependent).
Transformer X3 provides auxiliary power for the UVC. It is used
for the digital input and relay output circuits. If the controller LED’s
are responding properly but the fan will not run, transformer X3
may be defective. Check the voltage at the secondary of trans-
former X3; it should be approximately 24 VAC.
Erroneous Temperature Readings
If it is suspected that the UVC is operating using erroneous
temperature data, the following procedure may be used to check
the sensors:
1. Measure the temperature at the suspect sensor using an
accurate thermometer.
2. Determine the sensor’s analog input number. Refer to the
unit wiring diagram or to the input/output tables (Tables 11
through 17).
3. Remove the IDC connector from its UVC terminals and
measure the resistance of the sensor (through the IDC
connection). Using the thermistor chart (Table 18), compare
this value with the measured temperature.
If the measured resistance and temperature match, go on
to step 4.
Table 18. Thermistor Chart
°F Ohms Volts °F Ohms Volts °F Ohms Volts
15 16,104 4.145 77 3,000 2.373 139 761 0.932
16 15,627 4.124 78 2,927 2.343 140 746 0.917
17 15,166 4.102 79 2,857 2.313 141 731 0.902
18 14,720 4.080 80 2,789 2.283 142 717 0.888
19 14,288 4.057 81 2,723 2.253 143 703 0.874
20 13,871 4.034 82 2,658 2.223 144 689 0.859
21 13,467 4.011 83 2,595 2.194 145 676 0.846
22 13,076 3.988 84 2,534 2.164 146 662 0.831
23 12,698 3.964 85 2,474 2.135 147 649 0.818
24 12,333 3.940 86 2,416 2.106 148 637 0.805
25 11,979 3.915 87 2,360 2.077 149 625 0.792
26 11,636 3.890 88 2,305 2.049 150 613 0.779
27 11,304 3.865 89 2,251 2.020 151 601 0.766
28 10,983 3.839 90 2,199 1.992 152 589 0.753
29 10,672 3.814 91 2,149 1.965 153 578 0.741
30 10,371 3.788 92 2,099 1.937 154 567 0.729
31 10,079 3.761 93 2,051 1.909 155 556 0.717
32 9,797 3.734 94 2,004 1.882 156 546 0.706
33 9,523 3.707 95 1,959 1.855 157 535 0.694
34 9,258 3.608 96 1,914 1.828 158 525 0.683
35 9,002 3.653 97 1,871 1.802 159 516 0.673
36 8,753 3.625 98 1,829 1.775 160 506 0.661
37 8,512 3.597 99 1,788 1.750 161 496 0.650
38 8,278 3.569 100 1,747 1.724 162 487 0.640
39 8,052 3.540 101 1,708 1.698 163 478 0.629
40 7,832 3.511 102 1,670 1.673 164 469 0.619
41 7,619 3.482 103 1,633 1.648 165 461 0.610
42 7,413 3.453 104 1,597 1.624 166 452 0.599
43 7,213 3.424 105 1,562 1.600 167 444 0.590
44 7,019 3.394 106 1,528 1.576 168 436 0.580
45 6,831 3.365 107 1,494 1.552 169 428 0.571
46 6,648 3.335 108 1,461 1.528 170 420 0.561
47 6,471 3.305 109 1,430 1.505 171 413 0.553
48 6,299 3.274 110 1,398 1.482 172 405 0.544
49 6,133 3.244 111 1,368 1.459 173 398 0.535
50 5,971 3.213 112 1,339 1.437 174 391 0.527
51 5,814 3.183 113 1,310 1.415 175 384 0.518
52 5,662 3.152 114 1,282 1.393 176 377 0.510
53 5,514 3.121 115 1,254 1.371 177 370 0.501
54 5,371 3.078 116 1,228 1.350 178 364 0.494
55 5,231 3.059 117 1,201 1.328 179 357 0.485
56 5,096 3.028 118 1,176 1.308 180 351 0.478
57 4,965 2.996 119 1,151 1.287 181 345 0.471
58 4,838 2.965 120 1,127 1.267 182 339 0.463
59 4,714 2.934 121 1,103 1.247 183 333 0.456
60 4,594 2.902 122 1,080 1.227 184 327 0.448
61 4,477 2.871 123 1,058 1.208 185 321 0.441
62 4,363 2.839 124 1,036 1.189 186 316 0.435
63 4,253 2.808 125 1,014 1.170 187 310 0.427
64 4,146 2.777 126 993 1.151 188 305 0.421
65 4,042 2.745 127 973 1.133 189 299 0.413
66 3,941 2.714 128 953 1.115 190 294 0.496
67 3,842 2.682 129 933 1.097 191 289 0.409
68 3,748 2.651 130 914 1.079 192 284 0.384
69 3,655 2.620 131 895 1.062 193 280 0.389
70 3,565 2.589 132 877 1.045 194 275 0.382
71 3,477 2.558 133 859 1.028 195 270 0.376
72 3,392 2.527 134 842 1.012 196 266 0.371
73 3,309 2.496 135 825 0.995 197 261 0.364
74 3,228 2.465 136 809 0.980 198 257 0.359
75 3,150 2.434 137 792 0.963 199 252 0.353
76 3,074 2.404 138 777 0.948 200 248 0.348
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