White wire question

[Rsjean]

The white wire on my existing thermostat is AUX. Nest wants the white wire connected to W1. It would seem that W2/AUX would be the correct choice. All other wires are the same on my existing thermostat and the nest. It’s just this white wire confusion.

[Patrick_Caezza]

@Rsjean 

Do you have a Heat Pump System?

Post a picture of your current thermostat wiring

[Rsjean]

Thanks for the reply. Here is a picture of the original thermostat wiring.

[Rsjean]

 

[Patrick_Caezza]

@Rsjean 

Are the brown and white wires both in the AUX terminal?

Take a look at the control board of the furnace/air handler and see how those two wires are terminated there.

[Rsjean]

The brown wire is not used at all. I suspect that the house had a dual fuel unit at one time. The propane tank was removed and the HVAC replaced. It’s hard to see but the brown wire is actually just tucked back and out of the way in the picture.