An ADT wireless door and window sensor is a small two-part device, a sensor and a magnet, that tells the control panel when a door or window opens, and it runs on a small battery that needs replacing every few years. SafeWise's guide to ADT troubleshooting explains the signs: the control panel shows a low-battery message such as LOW BATT or BAT, and the sensor or panel chirps at intervals. The chirp can be silenced temporarily from the panel, often by pressing the OFF or the pound button, but the message returns until the battery is replaced.
The checks in more detail
To replace the battery, check the type inside the sensor or in its manual, because models differ, put the system into test or maintenance mode if the panel offers it, open the sensor's case by releasing the clip or sliding the cover, take out the old battery, noting its direction, and fit a fresh one the right way round. After closing the case, the sensor reports to the panel, and the message should clear.
Some panels need you to clear the trouble from the keypad. If the low-battery message does not clear, check that the case is shut so that the tamper switch is closed, that the battery is fresh and seated, and that the sensor is within range of the panel. IGotC's guide on beeping ADT sensors adds that a beeping sensor may also point to a signal problem, so check the placement.
The sensor and magnet should be within a few millimetres of each other when the door is closed, with the gap not more than about a quarter of an inch, which SafeWise mentions, and a sensor with a wider gap reports open. Replace the batteries in all sensors of the same age together, since they run down at similar times, and write the date inside. Dispose of old batteries at a recycling point and keep spare cells away from children. If a new battery does not fix the message, the sensor may need replacing.
Differential
Likely causes of “ADT Door/Window Sensor has power or battery problems”, and how to tell them apart
- 1
A weak battery
What separates it A low-battery message and chirp
How to confirm Replace the battery
- 2
A case not closed
What separates it The tamper switch is open
How to confirm Close the case firmly
- 3
The gap too wide
What separates it The sensor reports open
How to confirm Move the magnet within a quarter inch
- 4
A signal problem
What separates it The sensor beeps or drops out
How to confirm Move it nearer the panel
- 5
A failing sensor
What separates it The message returns after a new battery
How to confirm Ask the installer to replace it
Before you touch a setting
Record this first — changing settings destroys the evidence
- The battery type in the sensor
- The panel's message
- The gap between sensor and magnet
- The date of the last change
Try in this order
0 of 6 completedPut the system in test mode
ReversibleIf the panel offers it.
Open the sensor case
ReversibleRelease the clip or slide.
Replace the battery
ReversibleFresh, right way round.
Close the case
ReversibleAnd check the gap to the magnet.
Clear the message
ReversiblePer the panel's instructions.
Write the date inside
ReversibleAnd change the others of the same age.
Model-specific
What is true of this model and not of its siblings
- Quarter inch
- The sensor and magnet gap.
- Same-age sensors
- They run down together.
Stop boundary
When this stops being a self-service repair
- !If the message returns with a fresh battery, ask the installer to replace the sensor
- !If the panel alarms when you open it, tell the monitoring company
- !Replace sensors that fail repeatedly
Evidence ledger
Sources behind this answer
Exact questions
Common questions
How do I change the battery in an ADT door sensor?+
Open the case, swap the cell, close it and clear the message.
Why does it keep beeping?+
A weak battery or a signal problem.
How close must the magnet be?+
Within about a quarter of an inch.
Should I change all batteries at once?+
Sensors of the same age, yes.