TRANE Model#-TUC1D100A9601AE Serial #-14303JH12G No heat I found thermostat setting at 75 degrees with the space temperature at 72 degrees I troubleshoot the unit and found the unit in a fault code error (open pressure switch) I clean out the from the inducer motor to the flue reset the unit then ran the heating mode unit ran ok , cycle off the unit to clean the flame sensor I cycle the unit about 5 different times the unit ran ok each time, I recommend to the customer to have their discharge and intake lines protected with a screen mesh to prevent birds are other debris from getting into the line which will call the unit pressure switch from tripping Need parts