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 15
9 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
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