25
TROUBLESHOOTING / SERVICE CHECKS
Malfunction
Probable Cause
Corrective Action
Will not initiate cooling cycle
Delay prior to changeover
Controller in changeover from heat mode
4-minute purge cycle must complete
Thermostat has cooling anticipator (compensator)
Remove anticipator
Air
flow
too low over evaporator
Isolate and correct air
flow
problem
Bypass damper opening prematurely
Adjust bypass damper closed w/ all zone dampers open
Will not initiate heat calls
Delay prior to changeover
Controller in changeover from cool mode
3-minute purge cycle must terminate
Heating anticipator incorrectly set
Set anticipator to lowest setting
Bypass damper opening prematurely
Adjust bypass damper closed w/ all zone dampers open
Zone dampers will not close
Repair power source
Transformer VA too low
Replace w/ correct transformer
Dampers incorrectly wired
Correct damper wiring
No output on damper terminal(s)
Cycle power to controller. Verify thermostat inputs are correct.
If problem persists, replace controller
Zone damper remains closed
Initiate thermostat call
Triac shorted (Continuous 24V ac @ damper terminals) Replace controller
W2 will not energize
Discharge air temperature above 88° F.
Normal operation
(Heat Pump only)
Relay contact failure (W2 LED on)
Replace controller
Bypass damper opening prematurely
Adjust bypass damper closed w/ all zone dampers open
Controller in cool mode
Verify jumper JU1 position
Blower runs continually
Fan operation selected on any thermostat
Verify fan switch on all thermostats
Fan relay contacts in controller seized
Replace controller, check 24 V AC
Controller failure (0V dc on + and – w/ LAT removed) Replace controller
Cooling calls short cycle
LAT shorted (0V dc on + and – w/ LAT installed)
Replace LAT
LAT wiring shorted (0V dc on + and – w/ LAT installed)
Heating calls short cycle
LAT open (5V dc on + and – w/ LAT installed)
Replace LAT
LAT wiring open (5V dc on + and – w/ LAT installed) Repair LAT wiring
LAT SENSOR TEMPERATURE TO DC VOLTS / RESISTANCE CHART
46
1.686
61
2.078
76
2.474
91
2.855
106
3.204
121
3.512
136
3.777
151
3.999
45
1.661
60
2.052
75
2.447
90
2.830
105
3.222
120
3.493
135
3.761
150
3.986
44
1.635
59
2.025
74
2.421
89
2.806
104
3.159
119
3.474
134
3.744
149
3.972
43
1.610
58
1.999
73
2.396
88
2.781
103
3.137
118
3.454
133
3.728
148
3.958
42
1.585
57
1.972
72
2.370
87
2.756
102
3.114
117
3.434
132
3.711
147
3.944
41
1.560
56
1.946
71
2.343
86
2.730
101
3.092
116
3.414
131
3.694
146
3.930
40
1.535
55
1.919
70
2.316
85
2.705
100
3.070
115
3.394
130
3.676
145
3.915
160
4.113
39
1.510
54
1.893
69
2.289
84
2.680
99
3.046
114
3.374
129
3.659
144
3.901
159
4.101
38
1.486
53
1.873
68
2.263
83
2.655
98
3.022
113
3.353
128
3.641
143
3.886
158
4.089
37
1.461
52
1.841
67
2.237
82
2.629
97
2.999
112
3.332
127
3.623
142
3.871
157
4.076
36
1.437
51
1.814
66
2.210
81
2.603
96
2.975
111
3.311
126
3.605
141
3.856
156
4.064
35
1.413
50
1.788
65
2.184
80
2.578
95
2.952
110
3.290
125
3.587
140
3.840
155
4.052
34
1.389
49
1.762
64
2.158
79
2.552
94
2.928
109
3.269
124
3.569
139
3.825
154
4.039
33
1.365
48
1.737
63
2.131
78
2.526
93
2.904
108
3.247
123
3.550
138
3.809
153
4.026
LAT electrical interference (Applicable to spark ignition) Install shielded cable to LAT, terminate shield on C terminal ONLY
All thermostats will not call
Repair power source
32
1.341
47
1.711
62
2.105
77
2.500
92
2.879
107
3.226
122
3.531
137
3.793
152
4.013
TROUBLESHOOTING AND LAT CHART
°F DC Volts °F DC Volts °F DC Volts °F DC Volts °F DC Volts
°F DC Volts
°F DC Volts °F DC Volts °F DC Volts
Loss of 24V ac on R and C
Controller in heat mode
Controller in cool mode
Loss of 24V ac on TR1 And TR2
Zone not calling while mode is active
Repair LAT wiring
