Trane TCONT900AC43UA - Communicating Systems Reference

R - B 1
Solving Err 91 Comm Errors
Err 91 displayed at the Comfort Control ............................................................................................ 2
When Err 91 is displayed at the Comfort Control, thermostat will go to OFF................................... 2
Troubleshooting Err 91 displayed at the Comfort Control ............................................................... 3
Troubleshooting IND COMM ERR ...................................................................................................... 4
Inducer motor drive board LED functions......................................................................................... 4
Troubleshooting BLW COMM ERR....................................................................................................7
System communication troubleshooting .........................................................................................10
Communicating system voltage readings ........................................................................................14
Normal operating voltage ...............................................................................................................14
Voltage readings made at the furnace or air handler LVTB ............................................................15
Voltage readings made at the Comfort Control sub base ...............................................................15
Voltage readings made at the Outdoor Unit...................................................................................15
Voltage readings made at TAM .....................................................................................................15
Communicating voltage to blower motor and furnace inducer drive board ......................................15
Furnace IFC ...........................................................................................................................15
Air handler .............................................................................................................................15
Communicating Systems Reference
Section B