Error 126: Equipment Change Alert; Error 139: 24V Communication Mismatch; Miscellaneous Alert Codes; Pressure Switch Failure - Trane ACONT900AC43UA Service Manual

Alert Code Response

Error 126: Equipment change alert

Comfort Control = Err 126
User Interface = No Alert Displayed
Outdoor Unit Fault LED = No Fault Reported
Problem Description
• Equipment does not match value stored at startup
- When communicating systems are initially powered
the comfort control will auto discover and remember
all equipment (outdoor unit, indoor unit) reported on
the communication bus
- A Telephone Access Module (TAM) will not create
this alarm
Possible Causes/Solutions
• Outdoor unit breaker tripped
• OD transformer or fuse open
• Field low voltage wiring open to outdoor unit

Error 139: 24v communication mismatch

Comfort Control = Err 139
User Interface = 24v COM MSMTCH
Furnace Fault LED = 10 Flash
Problem Description
• Mode has been set incorrectly on User Interface
- This fault only applies to communicating 80%
furnaces
Possible Causes/Solutions
• Comfort control mode on the furnace user interface is
set for 24v when installed with communicating
comfort control
- If installed as part of a communicating system, the
comfort control mode must be set to communicating
(COMM)
R - A 18

Miscellaneous alert codes

Pressure switch failure

Comfort Control = No Error Code Displayed
User Interface = PS1 OPEN
Furnace Fault LED = 3 Flash
Problem Description
• First stage pressure switch will not close
Possible Causes/Solutions
• Pressure switch contacts stuck open
• Pressure switch tubing 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 = PS1 CLOSED
Furnace Fault LED = 3 Flash
Problem Description
• First 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 = PS2 OPEN
Furnace Fault LED = 3 Flash
Problem Description
• Second stage pressure switch will not close
Possible Causes/Solutions
• Pressure switch contacts stuck open
• Pressure switch tubing not connected or restricted
• Vent piping restricted or improperly sized
• Flue gas condensate backing up in secondary heat
exchanger