Connect a C-wire Adapter to Your Amazon Smart Thermostat

If your heating system doesn't have a power wire for the Thermostat, a C-wire adapter provides one.

Do you need a C-wire Adapter? Find out with the compatibility checker at amazon.com/amazonsmartthermostat. In the Compatibility information box, select Check compatibility.

We recommend using the C-wire Adapter most compatible with the Amazon Smart Thermometer. You can also refer to that adapter's installation instructions.

Important: Before starting work on the Thermostat or the heating and cooling system (HVAC), always switch off the power to the HVAC at the breaker box or the system's primary power switch. Verify the power is off before removing the device faceplate. Do not touch any exposed wire ends.
  1. With the Thermostat faceplate off, take a photo of the wiring and wire labels, for later reference.
  2. Go to your HVAC system and remove the cover to reveal the control board. Take a photo of the wiring, labels and terminal connections there for reference.
  3. Find and label the wires connected to these terminals:
    • G
    • W or W1 - If you have a heat pump, there may be wires at the O, B or O/B terminal instead of W.
    • R or Rc
    • Y or Y1
    If a terminal has multiple wires connected, label only the wire running to your Thermostat.
  4. Disconnect only the wires you just labeled from the control board.
  5. In the C-wire Adapter, insert the disconnected wires into these terminals on the "Thermostat" side of the adapter:
    • W or O/B wire to W terminal
    • G wire to C terminal
    • R or Rc wire to R terminal
    • Y or Y1 wire to K terminal
  6. Connect the wires from the "Equipment" side of the adapter to the matching terminals on the HVAC control board. Place the adapter near the control board and close the HVAC cover.
  7. At your Smart Thermostat, label the G wire as C, and label the Y wire as K. Disconnect those two wires and then reconnect them into the matching C and K terminals.
    When you're done wiring, you should have wires in the C and K terminals, and no wires in the Y or G terminals.
  8. Close the wire cover on the wall plate, then attach the Thermostat faceplate. Turn on the power to the HVAC system, at the breaker or system switch. If the Thermostat display shows SEt or the temperature, it's connected successfully.

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