No C-wire is common, and the Power Extender Kit (PEK) adapter is the solution. It lets the thermostat draw power from your HVAC system's control board.
- Safety First: Turn off your HVAC system at the master switch or circuit breaker. Confirm it's off by trying to turn on the heat or AC—you should feel nothing from the vents.
- Remove your old thermostat. Carefully disconnect and label each wire one at a time using the provided labels. Ignore any jumper wires between Rc, Rh, or R terminals.
- At your furnace control board, you'll install the PEK. The ecobee app provides customized wiring diagrams and videos for this exact step. Essentially, you'll connect the PEK module to the board, and it will create a virtual C-wire.
- Mount the ecobee backplate, run the wires through, and connect them as directed by the app, which will include the wire from the PEK.
IF THAT DIDN'T WORK: Double-check all wire labels and connections at both the thermostat and the control board. A single misplaced wire will prevent power. The app's guided setup is the most reliable resource.
HEADS UP: If you have multiple G wires or are adding accessories like a humidifier, specific wiring diagrams exist for those scenarios.