ADT's motion sensor article describes a pet-friendly sensor that alerts you when movement is detected inside your home and, with professional monitoring, notifies the monitoring center when the system is armed and it detects motion. It is set up in the ADT+ app: Menu, Devices, plus, ADT Devices, Sensors and Detectors, Motion Sensor, and you pick where you will use it; pair it with the Base before mounting.
The checks in more detail
Insert the CR123A battery only when setup begins, and mount it with the included double-sided tape after wiping the surface with an alcohol wipe, or with screws. If it does not detect movement, check it is online and has a fresh battery, that the system is armed in a mode that uses motion, that it faces the area at a suitable height and angle and that nothing blocks its view. Keep it away from heat sources, direct sun and vents that can trigger false alerts.
Being pet-friendly, it is tuned to ignore small animals but very large pets can still trigger, so test with the household. Use Test Mode to check the sensor reports. If it goes offline, follow the offline steps. Clean the battery contact if a low battery message appears with a new battery. Walk the route an intruder would take, slowly and quickly, and check the alert each time. Check again at a different time of day, since sun and heat change what triggers.
Adjust placement in small steps. A motion sensor is pet-friendly rather than pet-proof, so a large dog that jumps onto furniture near the sensor may still trigger it, and mounting it higher can help. Motion sensors cover rooms with windows or a hallway with none, as ADT describes, so choose the spot by what you want to cover and confirm coverage by walking, not by looking at a diagram.
Differential
Likely causes of “ADT sensors and detectors misses motion or records too many events”, and how to tell them apart
- 1
An unarmed mode
What separates it No motion alert arrives at all because the system is not armed in a mode that uses the motion sensor
How to confirm Arm the system in a mode that includes motion detection, such as the away mode, and try again
- 2
A weak battery
What separates it Movement in front of the sensor is missed because the battery is getting weak and detection is unreliable
How to confirm Replace the CR123A battery with a fresh one and test again by walking across the sensor's view
- 3
Heat or sun
What separates it False alerts happen when sun, a heater or a warm vent changes the temperature in front of the sensor
How to confirm Move the sensor away from heat sources, direct sun and vents so it sees people and not warm air
- 4
A poor angle
What separates it There are gaps in coverage because the sensor is mounted at the wrong angle or height for the room
How to confirm Adjust the mounting angle and height so that it covers the doorways and walkways you want to watch
- 5
An offline sensor
What separates it No motion reports reach the app because the sensor has gone offline from the Base
How to confirm Follow the offline steps for the sensor and add it again if it will not reconnect
Before you touch a setting
Record this first — changing settings destroys the evidence
- The system mode that was set when the motion was missed
- The age of the battery in the sensor
- Where and at what height the sensor is mounted
- The signal strength for the sensor in the app
Try in this order
0 of 7 completedCheck the mode
ReversibleCheck the mode first, because a motion sensor only raises an alert when the system is armed in a state that uses motion.
Check the battery
ReversibleCheck the battery, which is a single CR123A, and replace it if the sensor has been in use for a long time.
Check placement
ReversibleCheck the placement, including angle, height and heat: the sensor should face across a doorway or walkway and stay away from sun and heaters.
Wipe the mount surface
ReversibleWipe the surface where you will mount the sensor with an alcohol wipe, so the double-sided tape sticks and the sensor stays at the right angle.
Test in Test Mode
ReversibleTest in Test Mode by walking across the sensor's field of view and checking the app shows the movement, without setting off a real alarm.
Re-add if offline
ReversibleRe-add the sensor in the app if it is offline, pairing it beside the Base with a fresh battery before you mount it again.
Contact ADT
ReversibleContact ADT if it still misses movement or records too many events after these steps, giving the mode, position and battery age.
Model-specific
What is true of this model and not of its siblings
- Motion sensor
- Pet-friendly and battery powered.
- Mounting
- Tape or screws, after pairing.
Stop boundary
When this stops being a self-service repair
- !If it never detects motion with a good battery, contact ADT through chat
- !If pets trigger it, move it higher or reposition
- !If the sensor is offline and will not come back, remove it and add it again in the app
Evidence ledger
Sources behind this answer
Motion sensor setup and use.
Battery types and lives.
Offline meaning and fixes per device.
Removing and adding devices.
The company and its products.
Exact questions
Common questions
Is it pet-friendly?+
Yes, the ADT motion sensor is pet-friendly, so it is designed not to react to ordinary pet movement the way a basic sensor would.
What battery does it use?+
The motion sensor uses one CR123A battery, which is inserted when setup begins and replaced when a low battery message appears.
How do I mount it?+
You can mount it with double-sided tape or with screws, so pick whichever suits the wall and clean the surface first if you use tape.
When do I insert the battery?+
You insert the battery when setup begins, following the prompts in the ADT+ app, so that the sensor can pair with the Base.
Does it alert monitoring?+
With professional monitoring, a detected movement while the system is armed also notifies the monitoring center, not just your phone.
Can heat cause false alerts?+
Yes, heat and direct sun can cause false alerts, so keep the sensor away from radiators, vents and windows that catch the sun.
How long do sensor batteries last in use?+
Sensor batteries can last up to two years in use, though busy sensors and extreme temperatures shorten that.
How often should batteries be changed?+
ADT recommends changing sensor batteries annually, so that they are replaced before a low battery message ever appears.
What if a low battery message will not clear?+
If a low battery message will not clear after a new battery, delete the sensor and add it again after 24 hours.