Ok, on aux heat the answer is no. Don't have that feature. The air handler model is:
4TEC 3F4BB 1000AA which I inappropriately identified as the "heat pump". Wasn't thinking clearly.
I can open it up and take pictures later today. There is no wiring diagram on the outside. Would be nice to find some documentation on the web so will look there.
Thanks for everything.
Your model number is off by one and google gave me a hard time about it. LOL
48 not 4B in the middle which is the ton size of your unit which is 4 Ton by the way.
So you have a TRANE 4TEC3F48B1000AA
Here's a online manual, but you should find when you open the big access door on the unit it's also mounted on the inside. ( I also have a trane air-handler, but different model)
https://www.trane.com/Commercial/Uploads/Pdf/1111/2_4tec3.pdfI have attached the wiring diagram below, one un molested and the other I have circled the 120 to 24v transformer and traced over the common wire as it leads down to the connection block. The wire is BLUE inside the Air Handler and you'll notice coming out the transformer the power wire is red with a fuse 5 amp fuse before it gets to the connection block.
These two wires ultimately have to get to the RC/RH and C on the thermostat to power it up.
Judging by the info you gave us and the and the old thermostat connections I don't think any of this below really applies but I'll throw it out for more info or to double check anyways.
I'm very curious about the BLUE wire in the wall hooked up to "O" on the thermostat and would like to have more info on which wires go to where when you open the door on the Airhandler. Just want to make sure it doesn't go to the Blue wire inside the Air handler.
Reason is because without a heater and only single stage cooling and heating you really don't need 6 wires. In my Arizona house they powered the "O" and the "W" heating together (inside the air handler they were twisted together). They did this since there is no actual heater and anytime to turn on the heater "W" it powers the reverse valve at the same time and only at the same time. I can only assume yours might be the same, but don't think so based on your first post wiring description.