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TABLE 5
Defrost Control Board Diagnostic LEDs (5−Strike)
DS2
Green
DS1
Red
Condition
Possible Cause(s)
Solution
OFF
OFF
Power problem
No power (24V) to board termi-
nals R & C or board failure.
1
Check control transformer power (24V).
2
If power is available to board and LED(s) do
not light, replace board.
Simultaneous
SLOW Flash
Normal operation
Unit operating normally or in
standby mode.
None required.
Alternating
SLOW Flash
5−minute anti−short cycle
delay
Initial power up, safety trip, end of
room thermostat demand.
None required (Jumper TEST pins to override)
OFF
SLOW
Flash
Low Pressure Fault
1
Restricted air flow over indoor
or outdoor coil.
2
Improper refrigerant charge in
1
Remove any blockages or restrictions from
coils and/or fans. Check indoor and outdoor
fan motor for proper current draws.
OFF
ON
Low Pressure Lockout
(5 strikes)
2
Improper refrigerant charge in
system.
3
Improper metering device
installed or incorrect operation
fan motor for proper current draws.
2
Check system charge using approach & sub-
cooling temperatures.
3
Check system operating pressures and
SLOW
Flash
OFF
High Pressure fault
installed or incorrect operation
of metering device.
4
Incorrect or improper sensor
location or connection to sys
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
ON
OFF
High Pressure Lockout
(5 strikes)
location or connection to sys-
tem.
have secure connections to system to prevent
refrigerant leaks or errors in pressure and
temperature measurements.
SLOW
Flash
ON
Discharge Line Tempera-
ture Fault
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-
FAST
Flash
ON
Discharge Line Tempera-
ture Lockout (5 strikes)
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).
Simultaneous
FAST Flash
Ambient Sensor Problem
Sensor being detected open or shorted. Board will revert to time/temperature de-
frost operation. (System will still heat or cool).
Alternating
FAST Flash
Coil Sensor Problem
Sensor being detected open or shorted. Board will not perform demand or time/
temperature defrost operation. (System will still heat or cool).
ON
ON
Circuit Board Failure
Indicates that board has internal component failure. Cycle 24 volt power to board. If
code does not clear, replace board.
OFF
Fast
Flash
Discharge Sensor Fault
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
Fast
Flash
OFF
Discharge Sensor Lockout
(5 strikes)
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.
