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DS2
DS1
Condition
Green
Red
OFF
OFF
Power problem
Simultaneous
Normal operation
SLOW Flash
Alternating
5−minute anti−short cycle
SLOW Flash
delay
OFF
SLOW
Low Pressure Fault
Flash
OFF
ON
Low Pressure Lockout
(5 strikes)
SLOW
OFF
High Pressure fault
Flash
ON
OFF
High Pressure Lockout
(5 strikes)
SLOW
ON
Discharge Line Tempera-
Flash
ture Fault
FAST
ON
Discharge Line Tempera-
Flash
ture Lockout (5 strikes)
Simultaneous
Ambient Sensor Problem
FAST Flash
Alternating
Coil Sensor Problem
FAST Flash
ON
ON
Circuit Board Failure
OFF
Fast
Discharge Sensor Fault
Flash
Fast
OFF
Discharge Sensor Lockout
Flash
(5 strikes)
TABLE 5
Defrost Control Board Diagnostic LEDs (5−Strike)
Possible Cause(s)
No power (24V) to board termi-
nals R & C or board failure.
Unit operating normally or in
standby mode.
Initial power up, safety trip, end of
room thermostat demand.
1
Restricted air flow over indoor
or outdoor coil.
2
2
Improper refrigerant charge in
Improper refrigerant charge in
system.
3
Improper metering device
installed or incorrect operation
installed or incorrect operation
of metering device.
4
Incorrect or improper sensor
location or connection to sys
location or connection to sys-
tem.
This code detects shorted sensor or high discharge temperatures. If the discharge
line temperature exceeds a temperature of 300ºF (148ºC) during compressor op-
eration the board will de−energize the compressor contactor output (and the de-
eration, the board will de−energize the compressor contactor output (and the de-
frost output if active). The compressor will remain off until the discharge tempera-
ture has dropped below 225ºF (107ºC).
Sensor being detected open or shorted. Board will revert to time/temperature de-
frost operation. (System will still heat or cool).
Sensor being detected open or shorted. Board will not perform demand or time/
temperature defrost operation. (System will still heat or cool).
Indicates that board has internal component failure. Cycle 24 volt power to board. If
code does not clear, replace board.
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 resist-
ance If the sensor resistance is not ithin range after 90 seconds the board ill
ance. If the sensor resistance is not within range after 90 seconds, the board will
count one fault. After 5 faults, the board will lockout.
Page 13
Solution
1
Check control transformer power (24V).
2
If power is available to board and LED(s) do
not light, 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.
fan motor for proper current draws.
2
Check system charge using approach & sub-
cooling temperatures.
3
3
Check system operating pressures and
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
have secure connections to system to prevent
refrigerant leaks or errors in pressure and
temperature measurements.
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