18
TROUBLESHOOTING INFORMATION: UNITARY DIAGNOSTIC CODES
Symptoms of Abnormal
Operation (Legacy &
ComfortNet™ Thermostat)
Diagnostic/Status LED Codes
Fault
Description
ComfortNet™
Thermostat Only
Possible Causes
Corrective Actions Notes & Cautions
Green Yellow Red Red Y1 Message Code
x Air conditioner/heat pump fails
to operate.
x Integrated control module
diagnostic/status LED’s
display the indicated code.
x ComfortNet™ thermostat “Call
for Service” icon illuminated.
x ComfortNet™ thermostat
scrolls “Check Air Conditioner”
or “Check Heat Pump”
message.
5
Flashes
5
Flashes
OFF OFF
x Invalid
Memory
Card Data.
INVALID
MC DATA
d4
x Shared data on
memory card has
been rejected.
x Verify system type
(communicating or
legacy).
x Verify shared data is
correct for your
specific model; re-
populate data if
required.
x Wire system as
legacy system.
x Turn power OFF prior to
repair.
x Use memory card for
your specific model.
x Insert memory card
BEFORE turning power
ON. Memory card may
be removed after data is
loaded. Turn power
OFF before removing
memory card.
x Error code will be
cleared once data is
loaded.
x Very long run time.
x Four consecutive compressor
protector trips with average
run time between trips greater
than 3 hours.
x Compressor operating at high
speed and outdoor fan
operating at low speed
x Integrated control module
diagnostic/status LED’s
display the indicated code.
OFF 1 Flash OFF ON if call
present;
OFF if no
call
x Low Side
Fault.
LOW SIDE
FAULT
01
x Low refrigerant
charge.
x Restriction in liquid
line.
x Indoor blower motor
failure.
x Indoor thermostat set
extremely low.
x Verify refrigerant
charge; adjust as
needed.
x Check for restricted
liquid line;
repair/replace as
needed.
x Check indoor blower
motor; repair/replace
as needed.
x Check indoor
thermostat setting.
x Turn power OFF prior to
repair.
x Fault will clear after 30
consecutive normal
cycles.
x Fault may be cleared by
cycling 24VAC to
control.
x Replace with correct
replacement part(s).
x Compressor and outdoor fan
are off.
x Thermostat demand is
present.
x Integrated control module
diagnostic/status LED’s
display the indicated code.
ON 1 Flash OFF ON if call
present;
OFF if no
call
x Low
Pressure Cut
Out Trip.
LPS OPEN 01
x Low refrigerant
charge.
x Restriction in liquid
line.
x Indoor blower motor
failure.
x Indoor thermostat set
extremely low.
x Verify refrigerant
charge; adjust as
needed.
x Check for restricted
liquid line;
repair/replace as
needed.
x Check indoor blower
motor; repair/replace
as needed.
x Check low pressure
switch; repair/replace
as needed.
x Check indoor
thermostat setting.
x Turn power OFF prior to
repair.
x Replace with correct
replacement part(s).
x Compressor and outdoor fan
are off.
x Low pressure switch trip 3
times within same thermostat
demand.
x Thermostat demand is
present.
x Integrated control module
diagnostic/status LED’s
display the indicated code.
x ComfortNet™ thermostat “Call
for Service” icon illuminated.
x ComfortNet™ thermostat
scrolls “Check Air Conditioner”
or “Check Heat Pump”
message.
ON 1 Flash ON ON if call
present;
OFF if no
call
x Low
Pressure Cut
Out Lockout
(3 Trips).
LPS
LOCKOUT
01
x Low refrigerant
charge.
x Restriction in liquid
line.
x Indoor blower motor
failure.
x Indoor thermostat set
extremely low.
x Verify refrigerant
charge; adjust as
needed.
x Check for restricted
liquid line;
repair/replace as
needed.
x Check indoor blower
motor; repair/replace
as needed.
x Check low pressure
switch; repair/replace
as needed.
x Check indoor
thermostat setting.
x Turn power OFF prior to
repair.
x Must clear fault by
cycling 24VAC to
control.
x Replace with correct
replacement part(s).
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