When it is time to replace the battery in your door/window sensor, you will see an alert on your system panel
The QS1135-840 door/window sensor requires 2 CR2032 batteries, which can be purchased from Indiana Alarm, local hardware store, mass retailer, or battery store.
1. Locate the sensor with a low battery on either your system panel.
2. Leaving the sensor on the door/window, open the cover by inserting a screwdriver in the slot at the top of the sensor.
3. Remove the old batteries.
4. Make sure the area where the batteries are stored is clean and there is no corrosion.
5. Place 2 new CR2032 batteries into the sensor, ensuring the writing is facing up.
6. Put the cover back on starting with the opposite end from which it was opened. You should hear a snapping sound if it closes correctly.
7. Check if the low battery status has cleared.