Trane ACONT900AC43UA Service Manual page 275

Error 67: Temperature sensor fault
Comfort Control = Err 67
User Interface = No Alert Displayed
Outdoor Fault LED = 6 Flash
Problem Description
• Coil temperature sensor fault
Possible Causes/Solutions
• Coil Sensor open or shorted
- Zero or infinite resistance
• Coil Sensor out of range
- Compare resistance value of sensor to chart in
literature
• No output voltage from control board to sensor
- With sensor disconnected, 5vDC should be
measured on control board
Error 79: LPCO fault
Comfort Control = Err 79
User Interface = No Alert Displayed
Outdoor Fault LED = 7 Flash
Problem Description
• (19 SEER) Open low pressure switch
• (16 & 20 SEER) Low pressure cut-out open for third
time within same call (hard lock-out), cycle power to reset
- (Cooling) Suction pressure is below 50psig and OD
temp is above 55°
- (Heating) Suction pressure is below 25psig and OD
temp is above 10°
• (16 & 20 SEER) Low pressure cut-out fault (heat/cool
lock-out)
- (Cooling) Suction pressure below 50psig and OD
temp is below 55°
- (Heating) Suction pressure below 25psig and OD
temp is below 10°
Possible Causes/Solutions
• System low on charge
• (Cooling) Indoor airflow restriction
• (Heating) Outdoor airflow restriction
• Wiring to low pressure switch is either open or shorted
- If power is interrupted to outdoor unit an ERR79 may
be displayed on the comfort control because the low
pressure switch will not be discovered on
communication bus
Alert Code Response
Error 80: High pressure monitor fault
Comfort Control = Err 80
User Interface = No Alert Displayed
Outdoor Fault LED = 17 Flash
Problem Description
• High pressure monitor fault for fifth time within same
call (hard lock-out), cycle power to reset
- Liquid pressure has risen above 595 PSIG then fell
below 535 PSIG five times within the same call
Possible Causes/Solutions
• (Cooling) Faulty outdoor fan
• (Heating) Faulty indoor blower
• Refrigerant over charge
• (Cooling) Outdoor airflow restriction
• (Heating) Indoor airflow restriction
• Wiring to high pressure switch is either open or
shorted
Error 87: Roll-out fault
Comfort Control = Err 87
User Interface = ROLLOUT OPEN
Furnace Fault LED = 4 Flash
Problem Description
• Open flame rollout
Possible Causes/Solutions
• Air impingement on burners or flame
• Draft inducer not operating properly
• Restricted heat exchanger
• Low outlet gas pressure
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