Wiring guide
Amazon Smart Thermostat wiring for heat pump, no C wire
The Amazon Smart Thermostat works with this setup, but you’ll need an adapter or extra wire (details below).
A heat pump with R, Y, G, O/B and AUX has a reversing valve and backup electric heat but no C wire. Heat pumps are exactly where smart thermostats get picky about power. Read the full heat pump, no C wire guide for how to confirm your setup and mistakes to avoid.
Wiring diagram
Detected system: Heat pump, 1-stage compressor, 1-stage aux heat, fan, no C wire · 5 wires
Amazon Smart Thermostat
Works with an adapterNo C wire: use Amazon’s C-wire power adapter. Per Amazon’s guide, the G wire moves to C and the Y wire moves to K.
| Wire | Color | Job | Connect to | Note |
|---|---|---|---|---|
| R | red | 24 V power | R | |
| Y | yellow | Cooling, stage 1 | K | Adapter carries cooling + fan on this wire |
| G | green | Fan | C | Moves to C with the adapter |
| O/B | orange | Reversing valve (O/B) | O/B | |
| AUX | white | Auxiliary heat | W |
Install steps
- Turn off power to the furnace/air handler (switch or breaker) and the AC condenser. Confirm the old thermostat is dead.
- Photograph the old wiring, then label each wire with the letter it came off. Ignore short jumpers.
- Install the adapter at your furnace or air handler following its instructions, with power still off.
- Connect each wire to the Amazon Smart Thermostat terminal shown above. Cap unused wires one at a time.
- Restore power and finish setup in the app using the settings below.
- Test heat, cool and fan. If a breaker trips or equipment runs nonstop, power off and call a pro.
App settings to choose
- Reversing valve (O/B): set to O or B (O for most brands; B for Rheem, Ruud and some others).
- Equipment type: heat pump with auxiliary (electric strip) heat.
What you need
- Amazon Smart ThermostatThe thermostat itselfCheck price
- Amazon C-wire power adapterRequired without a C wireCheck price
As an Amazon Associate we earn from qualifying purchases, at no cost to you.
Confirm against the official Amazon install guide. The app also checks your wiring during setup.
Frequently asked questions
Where does each wire go on the Amazon Smart Thermostat?
R → R; Y → K; G → C; O/B → O/B; AUX → W.
Do I need a C wire for the Amazon Smart Thermostat?
No C wire: use Amazon’s C-wire power adapter. Per Amazon’s guide, the G wire moves to C and the Y wire moves to K.