OPERATION
Outdoor unit and indoor blower cycle on demand from the room thermostat. When the thermostat blower switch is moved to the ON position, the indoor blower operates continuously.
System Diagnostic Module
4AC16LT units contain a diagnostic module for trouble- shooting air conditioning system failures. By monitoring and analyzing data from the compressor and thermostat demand, the module can accurately detect the cause of electrical and system related failure without any sensors. If a system problem occurs, a flashing LED indicator communicates the failure code.
LED Description
POWER LED (Green) indicates voltage is present at the power connection of the module.
ALERT LED (Yellow) communicates an abnormal system condition through a unique flash code. The ALERT LED will flash a number of times consecutively, pause, and then repeat the process. The number of consecutive flashes correlates to a particular abnormal condition.
TRIP LED (Red) indicates there is a demand signal from the thermostat but no current to the compressor is de- tected by the module. The TRIP LED typically indicates the compressor protector is open or may indicate missing supply power to the compressor.
Interpreting the Diagnostic LEDs
When an abnormal system condition occurs, the diagnostic module displays the appropriate ALERT and/or TRIP LED. The yellow ALERT LED will flash a number of times consecutively, pause, and then repeat the process. To identify a flash code number, count the number of consecu- tive flashes. Refer to Table 9 on page 17 and Table 10 on page 18 for information on the flash codes.
Every time the module powers up, the last ALERT LED flash code that occurred prior to shutdown is displayed for 60 seconds. The module will continue to display the previous flash code until the condition returns to normal or 24VAC is removed from the module. TRIP and ALERT LEDs flashing at the same time means control circuit voltage is too low for operation.
24VAC Power Wiring
The diagnostic module requires a constant nominal 24VAC power supply. The wiring to the module’s R and C terminals must be directly from the indoor unit or thermostat.
Thermostat Demand Wiring
The diagnostic module requires a thermostat demand signal to operate properly. The thermostat demand signal input, labeled Y on the module, should always be con- nected to the compressor contactor coil so that when the coil is energized, the demand signal input is 24VAC. When the coil is not energized, the demand signal input should be less than 0.5VAC.
Miswired Module Codes
Depending on the system configuration, some ALERT flash codes may not be active. The presence of safety switches affects how the system alerts are displayed by the module.
Miswiring the diagnostic module will cause false LED codes. Table 11 on page 19 describes LED operation when the module is miswired and what troubleshooting action is required to correct the problem.
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