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How to reattach Nest Detect if it has fallen

If Detect or its open-close magnet falls off, it won’t be able to properly communicate activity to Google Nest Guard. You might see the following behavior:

  • Door or window always appears as “open” in the Nest app: Even when the door or window is physically closed, the app might think it’s open because Detect and the magnet are no longer within range of each other.

  • Poor motion detection: If Detect falls off a door or wall, it might land with its sensors pointing the wrong way or obstructed by the floor and furniture. Detect won’t be able to spot motion correctly until you remount and recalibrate it.


How to identify which piece fell off

On a door or window, Detect should look like
this picture. The open-close magnet is the
smaller piece that doesn’t move when the
door or window opens.

Although certain installations may look a
little different, keep in mind Detect and the
open/close magnet should both be present.

If either piece is missing, you’ll need to find it
and reattach it. If you can’t find the missing
piece, contact Nest for support.

Secure Detect mounted

On a wall installation, there won’t be an open-close magnet. You’ll only need to look for Detect.

How to reattach Detect or the open-close magnet

After you find the piece that fell off, look at the spot where it was originally installed. Depending on which part detached, follow the instructions below.

The backplate fell off along with Detect, or the magnet fell off

Detect has a mounting backplate. If the backplate was still attached to Detect when you found it, or if the open-close magnet fell off, you’ll need to remount it and then check Detect’s setup.

Here are some things to keep in mind:

  • If Detect had been mounted with the adhesive strip, you might want to re-attach it using a screw instead.

  • We included extra screws and adhesive strips with Nest Security, but if you need more, contact us for replacements.

  • Use only the screws included in the box. They’re precisely engineered to fit in our unique backplates, so we don’t recommend using other screws.

  • Don’t use adhesive strips, screws, backplates, or open-close magnets from other brands.

Once you’re ready to remount your Detect or magnet, follow these steps:

  1. If there’s any old adhesive still attached to the backplate, pry up one edge and gently pull the whole piece until it stretches then detaches. You might need to do this a few times for it to come off all the way.

    Note: Don’t use any solvents or cleaning fluids to dissolve the adhesive, as this could cause damage.

  2. Open the Nest app and select Settings Nest settings icon.

  3. Tap the Detect you’re remounting.

  4. Under Device Settings, select Check setup.

  5. The Nest app will walk you through the process of remounting the piece that fell off, including steps to check Detect’s setup afterward so it can sense activity properly.

Note: If you need some extra help with remounting Detect, see full instructions and more information at the following link:

How to install Detect >

Detect just fell out of it's backplate 

As long as the backplate is still securely attached to the wall, door or window, it’s easy to re-attach the part that fell off.

  1. Before snapping it back in, make sure Detect is correctly aligned:

    • On a door or wall, the Nest logo and light ring should be pointing down.

    • On a window, the Nest logo and light ring should be closest to the magnet, but depending on how you originally installed your Detect, they might not necessarily be pointing down.
  2. Simply snap Detect into its backplate. It should go right in.

Note: We designed Detect to snap securely into it backplate. If it repeatedly falls out, contact Nest Support for further troubleshooting.


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