I have a Trane XE60 furnace with a Trane air conditioning compressor for cooling. My thermostat has a yellow wire that runs to the furnace and then connects to another yellow wire that goes to my outside compressor. However, while both yellow wires are connected to each other, they are not connected to the Y terminal on the furnace controller.
My heater and air conditioner have worked for years with the wiring this way. My question is - will the system work any differently if I actually connect both yellow wires to the Y terminal?