4 Wire Old Honeywell Thermostat Wiring. Remove the wall screws holding up the thermostat before disconnecting the wiring to prevent the wires from falling into the wall. If you have a trane model thermostat and have a wire labeled x or b refer to your thermostat manual.
Ross suggests taking a picture of the wiring configuration to keep track of which wire goes where. But here is a list of the most common wire color mappings as seen in many four wire t stat setups. In this case we chose to give up control of the fan to power our honeywell wi fi t stat.
In this case we chose to give up control of the fan to power our honeywell wi fi t stat.
The table above provides a more complete list of honeywell thermostat wiring colors and their uses. Let s take a look at the g wire. Old honeywell thermostat wiring diagram source. There are only four wires going into the existing thermostat red green blue white.
