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Troubleshoot wired Nest Protect power problems

If you have a wired 120V Nest Protect, the Nest app will notify you if it loses power but is still connected to Wi-Fi. You'll also know your wired Nest Protect isn't receiving power when its small green power light is off.

Protect's backup batteries will keep it working

A wired Nest Protect comes with long-life backup batteries, so it should keep on working when you need them most. If your wired Nest Protect stops receiving power from the building's electrical wiring, it should automatically switch to backup battery power.

Even when it’s running off the backup batteries, your wired Nest Protect will stay connected to other Nest Protects in your home. It should continue to monitor smoke and carbon monoxide (CO) conditions and alert you in the event of an emergency or Heads Up alarm. It should also continue to send notifications to the Nest app when it alarms as long as the Wi-Fi network still works.

Fix wired Nest Protect power problems

 If you get a “Heads up! Power out“ message from your Protect smoke and CO alarm, follow these steps:

1. Check the breaker or fuse box

When power goes out to only a part of your home, one or more switches on the breaker box may not be turned on, or a fuse could be blown.

  • If you have a fuse box, check for blown fuses and replace them.
  • If you have a breaker box with switches, check that the switch controlling power to your Protect is switched on. Flip the switch off and on again. If your Protect’s green power light turns back on after you flip the switch, that was most likely the problem.
breaker box with text

2. Check the wiring

Wiring issues usually crop up during or right after installation, but wires can sometimes become disconnected later, especially if the connections weren’t securely terminated with a wire nut.

Note: If you had a professional install your Nest Protects, contact them to diagnose and fix wiring issues. A trained professional knows how to safely deal with high-voltage equipment and ensure proper connection for all wires. You can also contact a Nest Pro installer in your area.


Here are the steps to check your Nest Protect wiring. Refer to your Nest Protect User Guide for more wiring details.

1. Turn off the power

Protect yourself against high voltage. Switch off the breaker switch or remove the fuse. Double check that any lights, appliances or other electronics connected to the same circuit are off.

WARNING: Failure to turn off the power may result in serious electrical shock, injury or death.

2. Remove your Nest Protect

To remove your Nest Protect, gently twist it counterclockwise.

3. Check the power connector

Make sure the connector is fully inserted into the back of Nest Protect. If it wasn't, turn the circuit breaker to switch back on. If the small green light still doesn't illuminate, turn the circuit switch off again, and try step 4.

4. Check the wiring

Check that the power wire (usually black) and neutral wire (usually white) connections are connected to the right wires on Nest Protect's connector. Refer to your Nest Protect User’s Guide for more details.

There must be a solid contact between the power wires. Make sure that all wire connections are capped with a wire nut that has been twisted until secure.

5. Turn the power back on

Flip the circuit breaker switch back on, and check if the Protect's green power light is on. The status in the Nest app may take a few minutes to change, so it's best to check the light.

If your Nest Protect still hasn't turned back on, contact a local professional installer.

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