Carrier Transicold 69NT40-561-001, Operation And Service Manual, Page: 76 / 182

T-340 4–40
AL19
Discharge
Temperature
High
Discharge temperature
exceeds 135°C
(275°F) for 10 minutes
within the last hour.
Restrictions in the
refrigeration sys -
tem.
Ensure the Discharge
Service Valve is fully
open.
Open the Discharge Ser -
vice Valve as needed.
Check the unit for air
flow restrictions.
Clean or remove any de -
bris from coils.
Non-condens -
ables in the refrig -
eration system.
With the unit off allow
system to stabilize to
ambient temperature.
Check system pressure
against PT Chart for
134a, refer to Table 7–5 .
Correct as required, re -
fer to Refrigerant Charge
Section 7.7.1 .
Additional Alarms
such as AL16,
AL24.
Check compressor
operation.
If the alarm persists, it
may indicate a failing
compressor, replace the
compressor, refer to
COMPRESSOR Ser -
vice Section 7.8 .
AL20
Control
Contactor Fuse
(F3)
Control power fuse
(F3A or F3B) is open.
Check F3A, if the
fuse is open:
Check PA, PB, CH coils
for short to ground, if
short is found:
Replace the defective
coil.
Replace the fuse.
Check F3B, if the
fuse is open:
Check ESV coil resis -
tance at TP7 to TP9, if
short to ground, or if re -
sistance is less than 4
ohms, coil is defective.
Check CF, ES, EF, HR
coils for short to ground,
if short is found, coil is
defective.
Replace the defective
coil.
Replace the fuse.
Check Voltage at
QC1:
If voltage is present, it in -
dicates a defective mi -
croprocessor.
Refer to Controller Ser -
vice Section 7.23 .
AL21
Control Circuit
Fuse (F1/F2)
One of the 18 VAC
controller fuses (F1/F2)
is open. Refer to Cd08.
System Sensors Check system sensors
for short to ground.
Replace defective sen -
sor(s).
Wiring Check wiring for short to
ground.
Repair as needed.
Controller Controller may have an
internal short.
Replace controller, refer
to Controller Service
Section 7.23 .
AL22
Evaporator IP
Evaporator motor inter -
nal protector (IP) is
open.
Evaporator Motor Shut down unit, discon -
nect power, & check
Evaporator Motor IP at
plug connection pins 4 &
6.
Replace defective evap -
orator fan motor, refer to
EVAPORATOR FAN
MOTOR Service Sec -
tion 7.15 .
AL23
Loss of Phase B
Controller fails to de -
tect current draw.
Incoming Power Check incoming power
source.
Correct power source as
required.
AL24
Compressor IP
Compressor internal
protector (IP) is open.
Compressor Shut down unit discon -
nect power, & check re -
sistance of compressor
windings at contactor
T1-T2, T2-T3.
Monitor unit, if alarm re -
mains active or is repeti -
tive replace the
compressor at the next
available opportunity, re -
fer to COMPRESSOR
Service Section 7.8 .
Table 4–6 Controller Alarm Indications
Alarm Code Cause Components Troubleshooting Corrective Actions