Low Flame Signal; Twinning Error - Trane ACONT900AC43UA Service Manual

Pressure switch failure
Comfort Control = No Error Code Displayed
User Interface = PS2 CLOSED
Furnace Fault LED = 3 Flash
Problem Description
• Second stage pressure switch closed when the switch
should be open
Possible Causes/Solutions
• Pressure switch contacts stuck closed
• Draft inducer motor running with no call for heat
• Improper wiring to pressure switch
Pressure switch failure
Comfort Control = No Error Code Displayed
User Interface = PS3 OPEN
Furnace Fault LED = 3 Flash
Problem Description
• Third stage pressure switch will not close
Possible Causes/Solutions
• Pressure switch contacts stuck open
• Pressure switch tubing either not connected or
restricted
• Vent piping restricted or improperly sized
• Flue gas condensate backing up in secondary heat
exchanger
Pressure switch failure
Comfort Control = No Error Code Displayed
User Interface = PS3 CLOSED
Furnace Fault LED = 3 Flash
Problem Description
• Third stage pressure switch closed when the switch
should be open
Possible Causes/Solutions
• Pressure switch contacts stuck closed
• Draft inducer motor running with no call for heat
• Improper wiring to pressure switch
Alert Code Response

Low flame signal

Comfort Control = No Error Code Displayed
User Interface = LO FLAME SNS
Furnace Fault LED = 8 Flash
Problem Description
• Flame current is low, but still strong enough to allow
operation
- 1.0 micro amp is the minimum flame current to
allow operation
Possible Causes/Solutions
• Flame sensor needs to be cleaned
• Flame sensor not properly positioned in flame
• Flame sensor wire has high resistance
• Low gas pressure causing weak flame

Twinning error

Comfort Control = No Error Code Displayed
User Interface = TWIN ERROR
Air Handler Fault LED = 8 Flash
or
Furnace Fault LED = No Fault Reported
Problem Description
• Multiple variable speed indoor units twinned together
Possible Causes/Solutions
• Variable speed indoor units cannot be twinned
R - A 19