Security Services & Features FAQs

How do I replace a door/window sensor battery?

When the battery in your door/window contact needs to be replaced, a “zone trouble” indicator will appear on your alarm keypad and/or “sensor trouble” indicator will appear on your ADT Command or Pulse device. You should replace the battery as soon as these indicators appear.

A door and window contact requires (1) CR123 3 volt battery (in some systems, the door and window contact will be a very slim device and will contain a single, CR2032 battery). This battery can often be purchased at your local hardware, mass retailer or battery store.

  1. Before you replace the battery, put your system into test mode to prevent false alarms.
    1. Log into and select Alarm System from the menu, then click on the System Test tab.
    2. Select the desired duration of the test period, then click Start Test Mode.  You can also call 800-ADT-ASAP or click on Chat with an Agent to put your system into test mode. 
  2. To change the battery, use a flathead screwdriver to push in the tab on the end of the contact. An arrow on the front of the contact points to where the tab is located. Replace the battery, observing the proper polarity. Then, replace the front cover by snapping it into place.
  3. The security system may need to be reset by entering the disarm command twice
  4. Remember to remove the system from Test Mode.Go to and click on  Alarm System from the menu, then click on the System Test tab. Click on End Test Mode to remove the system from test mode and restore operations.

To view videos on hoe to change your sensor battery, please visit our Video Library.