Check the battery by removing it and reinserting it into the Sensor. If your Sensor's LED does not light up, insert a new CR123A battery. (See Battery Replacement instructions in the ADT Motion Sensor article.) You may need to remove the Sensor and re-add it to your system. Please fol...
Refer to the Battery Replacement instructions below. If they have not been changed recently, it is time to change the batteries in the Detector. You will need three CR123A batteries. To obtain new batteries, you can do one of the following: Click the chat icon to order your battery or ...