EcoGuide · Smart Thermostats · Published 2026-10-01 · 1,100 words
Amazon Smart Thermostat Not Heating or Cooling: Amazon’s Checks, in Order
The Short Answer
When an Amazon Smart Thermostat will not start the heat or the air conditioning, Amazon’s troubleshooting starts in the same place both times: the wiring. This thermostat works out what kind of system you have from which wires are connected, so one wire in the wrong terminal can make a whole mode disappear.
| What happens | Most likely cause | Section |
|---|---|---|
| Cool mode is missing in the Alexa app | Y wire in the wrong terminal, or R/RC mix-up | No cooling |
| Heat will not come on | W (or Y and O/B) wiring, or the R jumper | No heat |
| Heat when you ask for cool, or the reverse | Heat pump reversing valve set the wrong way | Wrong air |
| It says Delayed Start | Normal compressor protection | Delayed Start |
| Screen is blank | No power | Blank screen |
Before touching wires: Amazon says to switch off power to the heating and cooling system at the breaker or the system switch, and confirm it is off (the thermostat screen goes blank). If you are not comfortable with low-voltage wiring, call an HVAC company.
First, the Quick Test
Set the mode and ask for a clear change. For heat, Amazon says to press the mode button until the flame icon lights, then raise the temperature 1 or 2 degrees above the current reading. For cooling, select Cool in the Alexa app and set the temperature lower than the room. Then go and look at the outdoor unit. If nothing starts after a few minutes, work through the sections below.
No Heat
Amazon’s heat troubleshooting in order:
- Work out the system type. With heat running, check the outdoor unit. If it is on and blowing air, you have a heat pump; if not, it is a conventional system (furnace or boiler).
- Check R and RC. One R wire goes in the R terminal with the jumper switch up. If you have both R and RC wires, each goes in its own terminal and the jumper goes down.
- Check the heat wires. Conventional system: W, R, Y, G and C in their matching terminals. Heat pump: Y, O/B, R, G and C, and no wire in W.
- Compare with the app. In the Alexa app open the thermostat’s settings, then Thermostat Configurations → Connected wire map. A conventional system should show a W connection; a heat pump should show Y and O/B.
- If you moved any wire, reset the thermostat and run setup again so it re-detects the system.
For a heat pump with electric backup heat, Amazon says the backup heat wire belongs in W2, not W.
No Cooling
From Amazon’s cooling troubleshooting:
- Y wire in the C terminal. If that has happened, the thermostat treats the system as heat only and Cool mode does not appear in the app at all.
- Y at both ends. The wire on the thermostat’s Y terminal should be the same colour wire on the Y terminal of the furnace or air handler control board.
- R and RC swapped or doubled up. With both wires, R goes to R and RC to RC; otherwise the thermostat may see the system as heat only or cool only. A single R or RC wire goes in R.
- Wire saver module. If one is fitted, it should connect to the K terminal.
- Cooling and backup heat running together on a heat pump points to the Y, C and W connections.
- App and wall disagree. If the Connected wire map does not match the wires on the wall plate, reset and set up again.
Wrong Air: Heat in Cool Mode, or Cool in Heat Mode
On a heat pump this is the reversing valve setting. Amazon’s fix is in the Alexa app: Devices → Thermostat → your thermostat → Device Settings → Thermostat Configuration → HVAC Type → Reversing Valve, then switch it from O to B or from B to O. When the thermostat display shows “APP”, press the Mode button on the thermostat to accept the change.
The background, and the same fix for other brands, is in heat pump heating instead of cooling.
When the Wiring Is Right and It Still Will Not Run
If the thermostat is calling, the wires match and the equipment stays off, the fault is likely at the equipment: a tripped breaker, an outdoor disconnect, or a failed part. Work through heat pump not turning on or thermostat clicks but nothing happens. Amazon’s own final step is to contact its customer support, and for heat pump faults an HVAC specialist.
Free: Home Energy Audit Checklist (PDF)
A two-page, room-by-room checklist for finding air leaks, standby power and heating and cooling waste yourself, in the order that pays back fastest. Get it now, plus new fix guides by email. Unsubscribe any time.
By signing up you agree to receive emails from EcoHome Intelligence. See our Privacy Policy.
Frequently Asked Questions
Why is my Amazon Smart Thermostat not turning on the heat?
Amazon says to check the wiring: the R wire and jumper position, then W for a conventional system or Y and O/B for a heat pump, and compare them with the Connected wire map in the Alexa app. If you move a wire, reset and set up again.
Why is there no Cool mode on my Amazon Smart Thermostat?
Amazon says that if the Y wire is connected to the C terminal, or R and RC are not in their matching terminals, the thermostat recognises the system as heat only and cooling will not appear in the app.
Why does my Amazon Smart Thermostat blow cold air on heat?
On a heat pump the reversing valve setting is probably reversed. In the Alexa app go to Thermostat Configuration, HVAC Type, Reversing Valve and switch O to B or B to O.
Do I need to reset my Amazon Smart Thermostat after moving a wire?
Yes. Amazon says to reset the thermostat and run setup again after moving any wires, so it detects the system correctly.
Related Guides
- Amazon thermostat says Delayed Start — normal delay vs a real fault
- How to reset an Amazon Smart Thermostat — partial and full reset
- Heat pump heating instead of cooling — the O/B setting explained
- Smart thermostat troubleshooting — every fix guide by symptom
