Indoor Blower Motor would not turn off in any mode. Furnace would heat would work fine and shut down "except" the indoor blower continued to run. I replaced the Stat with the same result. So I reinstalled old Stat. Replaced the Intel-Ignition Circuit board 50A65-475 with the White_Rodgers recommended 50A65-843... and all went well all night... (yes I installed jumper as required on Trane)... BUT... (24 hours later)

NOW... the furnace works as designed for (1) cycle as designed... then when stat calls for heat again all works fine, EXCEPT when indoor blower is called to turn on(blow the warm air to the registers) I can hear the relay (I guess)clicking on then off repeatedly. This is EXACTLY what was going on just before... when the Blower would not turn off and run continuously... BEFORE I replaced the Original "Lemon" Intel-Ignition Circuit Board.
The furnace is only 3 years old. It's installed in my attic. I did notice the Indoor Fan Capacitor shows some very small signs of oil seepage? Is not the Capacitor only used when using the A/C? If so then this should not be the problem, ay? Again the furnace is only (3) years old. Nothing runs like a Trane? I'm running out of ideas.
To recap... the indoor blower is trying to start but just ain't.

Check for a brown-out condition (low line voltage) when the blower is attempting to start. If present, check all electrical connections in the power supply circuit to the unit.

Jeep97, I have similar issue with a TRANE TUE060 furnace. Blower works with AC . Blower also works when thermostat fan is set to ON. However, when heat is on, the blower does not work and the furnace gets overheated, guess because of the lack of air flow. Any idea ?

Thanks
Richard