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DS2
DS1
Condition / Code
Green
Red
Off
Power problem
Simultaneous
Normal operation
SLOW flash
Alternating
5-minute anti-short cycle
SLOW flash
delay
Simultaneous
Ambient sensor problem
FAST flash
Alternating
Coil sensor problem
FAST flash
On
Circuit board failure
Fault & Lockout Codes (Each fault adds 1 strike to that code's counter; 5 strikes per code = LOCKOUT)
SLOW
Off
Low pressure fault
flash
Off
On
Low pressure LOCKOUT
SLOW
Off
High pressure fault
flash
On
Off
High pressure LOCKOUT
SLOW
Discharge line
On
flash
temperature fault
FAST
Discharge Line
On
flash
Temperature LOCKOUT
FAST
Off
Discharge sensor fault
flash
FAST
Discharge sensor
Off
flash
LOCKOUT
506468-01
Control Board Diagnostic LEDs
Possible Cause(s)
No power (24V) to board
terminals R & C or board
failure.
Unit operating normally or in
standby mode.
Initial power up, safety trip,
end of room thermostat
demand.
Sensor being detected open or shorted or out of temperature range. Board will revert
to time/temperature defrost operation. (System will still heat or cool)
Sensor being detected open or shorted or out of temperature range. Board will not
perform demand or time/temperature defrost operation. (System will still heat or cool)
Indicates that board has internal component failure. Cycle 24V power to board. If
code does not clear, replace board.
1. Restricted air flow over
indoor or outdoor coil.
2. Improper refrigerant
charge in system.
3. Improper metering device
installed or incorrect
operation of metering
device.
4. Incorrect or improper
sensor location or
connection to system.
This code detects shorted sensor or high discharge temperatures. If the discharge
line temperature exceeds a temperature of 300°F (148°C) during compressor
operation, the board will de-energize the compressor contactor output (and
the defrost output if active). The compressor will remain off until the discharge
temperature has dropped below 225°F (107°C).
The board detects open sensor or out of temperature sensor range. This fault is
detected by allowing the unit to run for 90 seconds before checking sensor resistance.
If the sensor resistance is not within range after 90 seconds, the board will count one
fault. After 5 faults, the board will lockout.
Table 6. Control Board Diagnostic LEDs
Issue 1946
Solution
Check control transformer power (24V).
1
If power is available to board and LED(s) do not light,
2
replace board.
None required.
None required (Jumper TEST pins to override)
1. Remove any blockages or restrictions from coils
and/or fans. Check indoor and outdoor fan motor
for proper current draws.
2. Check system charge using approach & sub-
cooling temperatures.
3. Check system operating pressures and compare
to unit charging charts.
4. Make sure all pressure switches and sensors
have secure connections to system to prevent
refrigerant leaks or errors in pressure and
temperature measurements.
Page 17 of 24
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