The W wire is connected to your heating system. If your thermostat controls your heat, you will have a white wire. The Y wire is yellow and connects to your air conditioning compressor. The G wire is green and connects to the fan. Rc and Rh: The Related searches for 1 wire thermostat wiring diagram thermostat schematic diagramthermostat wiring schematic diagramdiagram of a thermostata c thermostat wiring diagramthermostat wiring diagram heat onlywiring diagram for hvac thermostatthermostat connection diagramfurnace thermostat wire diagram