If your Nest Protect smoke and CO alarm is giving false alarms, shows offline in the app, or won't connect to your network, this guide covers the most common problems and solutions.
False Smoke Alarms
When the alarm triggers without smoke:
- Steam from showers can trigger smoke sensors - move away from bathrooms
- Cooking smoke/steam is the most common cause of false alarms
- Clean the detector vents with compressed air
- Ensure detector isn't near kitchens or high-humidity areas
- Check for dust buildup on the sensor
- Avoid placing near fireplaces or candles
False CO Alarms
For carbon monoxide false alarms:
- First, take any CO alarm seriously - evacuate if unsure
- Check for actual CO sources (gas appliances, vehicles in garage)
- Ensure proper ventilation in the area
- Don't place near gas stoves or ovens
- CO sensors can be triggered by some chemicals/solvents
- Replace detector if nearing end of 10-year lifespan
Detector Shows Offline in App
When Nest Protect won't connect:
- Check your WiFi network is working
- Verify the detector is within WiFi range
- Restart your router
- Remove and re-add the detector in Google Home
- Check detector battery level (wired models have backup battery)
- Ensure you have a strong 2.4GHz signal (required)
Yellow Light or Warning
Understanding the yellow status light:
- Yellow typically means the detector needs attention
- Open Google Home app to see the specific warning
- Could indicate low battery, sensor issue, or WiFi problem
- Run a manual test by pressing the button
- Check for expired sensor (lifespan is ~10 years)
- Yellow during test means Heads-Up warning detected something
Nest Protect Won't Connect to WiFi
During setup or reconnection:
- Nest Protect only works with 2.4GHz networks
- Check WiFi password doesn't have special characters
- Move closer to router during setup
- Ensure your network isn't blocking new devices
- Try forgetting and reconnecting in the app
- Reset the detector and set up again
Sound Check or Monthly Test Issues
If automatic tests aren't working:
- Sound Check requires WiFi connection
- Tests happen automatically at selected time
- Ensure "Nightly Promise" is enabled in settings
- Run manual test by pressing the button
- Check battery level - low battery prevents tests
- Multiple Protects test together via Wireless Interconnect
Battery Issues (Battery Model)
For battery-powered Nest Protect:
- Uses 6 Energizer Ultimate Lithium AA batteries
- Don't use rechargeable or other battery types
- Battery life is typically 5 years
- Replace all batteries at once
- Check battery level in Google Home app
- Low battery warning gives advance notice
Wired Model Power Issues
For wired Nest Protect:
- Check circuit breaker hasn't tripped
- Verify wiring connections are secure
- Backup battery should be replaced periodically
- Wired power LED should be green when powered
- Check voltage at junction box if issues persist
Factory Reset Nest Protect
For persistent issues:
- Press and hold the button for 10+ seconds
- The detector will speak, continue holding
- Release when it says "resetting"
- Remove from Google Home app
- Set up again as new device
- Note: This doesn't extend the 10-year sensor life