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TROUBLESHOOTING INFORMATION: UNITARY DIAGNOSTIC CODES
Diagnostic/Status LED Codes
ComfortNet™
Thermostat Only
Symptoms of Abnormal
Operation (Legacy &
ComfortNet™ Thermostat)
Green Yellow Red Red Y1
Fault
Description
Message Code
Possible Causes
Corrective Actions Notes & Cautions
x Four consecutive compressor
protector trips with average run
time between trips greater than 1
minute and less than 15 minutes.
x Low pressure and high pressure
switches are closed.
x Integrated control module
diagnostic/status LED’s display
the indicated code.
OFF 2 Flashes OFF ON if
call
present
; OFF if
no call
x High Side
Fault
HIGH SIDE
FAULT
02
x Blocked condenser
coil.
x Outdoor fan not
running.
x Check and clean
condenser coil.
x Check outdoor fan
motor;
repair/replace as
needed.
x Check outdoor fan
motor wiring;
repair/replace as
needed.
x Check outdoor fan
motor capacitor;
replace as needed.
x Turn power OFF
prior to repair.
x Fault will clear after
4 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 2 Flashes OFF ON if
call
present
; OFF if
no call
x High
Pressure Cut
Out Trip
HPS OPEN 02
x Blocked condenser
coil.
x Outdoor fan not
running.
x Check and clean
condenser coil.
x Check outdoor fan
motor;
repair/replace as
needed.
x Check outdoor fan
motor wiring;
repair/replace as
needed.
x Check outdoor fan
motor capacitor;
replace as needed.
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 2 Flashes ON ON if
call
present
; OFF if
no call
x High
Pressure Cut
Out Lockout
(3 Trips)
HPS
LOCKOUT
02
x Blocked condenser
coil.
x Outdoor fan not
running.
x Check and clean
condenser coil.
x Check outdoor fan
motor;
repair/replace as
needed.
x Check outdoor fan
motor wiring;
repair/replace as
needed.
x Check outdoor fan
motor capacitor;
replace as needed.
x Turn power OFF
prior to repair.
x Must clear fault by
cycling 24VAC to
control.
x Replace with correct
replacement part(s).
x Run time for last 4 cycles is less
than 3 minutes each.
x Compressor protector has not
tripped.
x Low pressure and high pressure
switches are closed.
x Integrated control module
diagnostic/status LED’s display
the indicated code.
OFF 3 Flashes OFF ON if
call
present
; OFF if
no call
x Short Cycling
CMPR
SHRT
CYCLE
03
x Intermittent thermostat
demand.
x Faulty compressor
relay.
x Check thermostat
and thermostat
wiring;
repair/replace as
needed.
x Check compressor
relay operation;
replace control as
needed.
x Turn power OFF
prior to repair.
x Fault will clear after
4 consecutive
normal cycles.
x Fault may be
cleared by cycling
24VAC to control.
x Replace with correct
replacement part(s).
x Minimum
compressor runt
time is changed from
30 seconds to 3
minutes.
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