ADT sensors are added through the ADT+ app after the Base is set up. Open the app, sign in, choose Menu, Devices, the plus sign, ADT Devices and Sensors and Detectors, then the sensor type, and follow the prompts; the system must be disarmed to add a device. ADT advises pairing the sensor to the Base before mounting it, so hold it near the Base while pairing and fit the battery when the setup asks, since the motion sensor's battery should not be inserted until setup begins. Name the sensor and choose where it will be used.
Then mount it: the motion sensor uses double-sided tape after an alcohol wipe or screws, and door and window sensors use a sensor and magnet aligned across the gap. Test it with the system disarmed and in Test Mode.
The checks in more detail
If pairing fails, check the battery type and seating, move closer to the Base, keep the Base central and clear, and try again; a device previously paired must be removed from its old account first. If the low battery message appears after setup, clean the contact. Smoke and CO detectors and sirens follow their own articles. ADT lists a setup support phone line. Pair one sensor at a time and label it in the app straight away.
If pairing works near the Base but not at the mounting spot, the spot is the problem. Pair when you are not rushed. The battery for the motion sensor should not go in until setup starts, so if you fitted it early, take it out and start again from the app. Check the sensor's battery type against ADT's list before you start, since a wrong cell that fits is a common cause of a sensor that pairs and then drops.
Differential
Likely causes of “ADT sensors and detectors will not complete setup or pairing”, and how to tell them apart
- 1
A misseated battery
What separates it Pairing fails again and again because the battery is not seated properly in the sensor
How to confirm Reseat the battery so that it sits firmly on both contacts and try to pair the sensor again
- 2
Distance
What separates it The app cannot find the sensor because it is too far from the Base when you try to pair it
How to confirm Pair the sensor right beside the Base, then move it to its final position once it is added
- 3
Armed system
What separates it The app refuses to add a device because the security system is armed at that moment
How to confirm Disarm the system first, then add the sensor from the Devices menu in the app
- 4
A device paired elsewhere
What separates it The sensor will not add because it is still paired with another account or an old Base
How to confirm Remove it from the old account or Base first, then pair it with your new Base as a new device
- 5
A dirty mount surface
What separates it The sensor falls off the wall because the surface it was stuck to was dusty or greasy
How to confirm Wipe the surface with alcohol, let it dry and fix the sensor again with fresh double-sided tape
Before you touch a setting
Record this first — changing settings destroys the evidence
- The type of sensor and the battery you fitted
- How far the sensor is from the Base when you pair it
- Whether the system is armed or disarmed
- Whether the sensor was paired before on another account
Try in this order
0 of 7 completedDisarm the system
ReversibleDisarm the system before adding anything, because ADT does not let you pair new devices while the system is armed.
Choose the sensor type
ReversibleChoose the sensor type in the app under Sensors and Detectors, so that the app shows the right pairing instructions for that sensor.
Pair beside the Base
ReversiblePair the sensor right beside the Base and fit the battery when the app asks you to, which starts the pairing at the right moment.
Name and place it
ReversibleName the sensor and place it in the app, choosing a room name you will recognize later when an alert or event appears.
Mount it
ReversibleMount the sensor with tape or screws only after it has paired, and check it still reports from its final position.
Test in Test Mode
ReversibleTest the sensor in Test Mode to confirm it reports to the Base, and adjust its position if the signal is weak.
Contact ADT
ReversibleContact ADT if pairing fails after these steps, and tell them the sensor type, battery and what the app displayed.
Model-specific
What is true of this model and not of its siblings
- Pairing
- Done beside the Base.
- Mounting
- After pairing.
- Other models this page answers
- These steps also fit models Heat Detector, Live Light, Premium Door/Window Sensor, Smoke and Carbon Monoxide Detector, Smoke Detector.
Stop boundary
When this stops being a self-service repair
- !If pairing keeps failing, contact ADT through chat
- !If a sensor was second-hand, ask for removal
- !If a battery message appears after setup, clean contacts
Evidence ledger
Sources behind this answer
Motion sensor setup and use.
Removing and adding devices.
Battery types and lives.
Offline meaning and fixes per device.
The company and its products.
Exact questions
Common questions
Where do I add a sensor?+
Add a sensor from Devices in the ADT+ app by tapping the plus sign and choosing ADT Devices, then Sensors and Detectors.
Should I pair before mounting?+
Yes, pair the sensor before you mount it, because pairing is easier beside the Base and you can check the connection first.
When do I insert the motion battery?+
For the motion sensor, insert the battery when setup begins and the app tells you, because that is what starts the pairing.
What if it will not pair?+
If it will not pair, reseat the battery and move the sensor closer to the Base, then try again from the beginning of the setup steps.
Should I test?+
Yes, test the sensor in Test Mode once it is added and mounted, so you know it reports to the Base without setting off an alarm.
Is there a phone line for setup?+
Yes, ADT has a phone line for setup, which is worth calling if the sensor still will not pair after these checks.
Can a dirty motion sensor cause low battery?+
Yes, residue from the protective battery tab can cause a low battery reading on a motion sensor, so clean the contacts.
What do I clean it with?+
Clean the battery contacts with an alcohol swab or wipe, and let them dry completely before you refit the battery.
What must the system be in before troubleshooting?+
The system should be disarmed and in Test Mode before you troubleshoot, so that nothing you do triggers a real alarm.