Overview

This article explains how to replace the battery in a Honeywell/Resideo PROSIXCT door/window contact sensor.


Required Materials

  • One (1) CR123A 3V lithium battery 
  • Small flathead screwdriver (optional)


Where to Purchase the Battery

A CR123A 3V lithium battery is commonly available at:

  • Hardware stores
  • Home improvement stores
  • Electronics retailers
  • Online marketplaces such as Amazon

Procedure

  1. Locate the PROSIXCT sensor on the door or window.
  2. Press the release tab at the bottom of the sensor and slide it off the mounting bracket.
  3. Separate the front and back halves of the sensor to access the battery compartment.
  4. Remove the old battery.
  5. Wait approximately 10 seconds.
  6. Insert a new CR123A 3V lithium battery, ensuring the polarity (+/-) matches the markings inside the sensor.
  7. Reassemble the sensor and slide it back onto the mounting bracket until it clicks into place.
  8. Arm the alarm system, then disarm it using a valid user code.

Verification

  • Wait a few minutes for the panel to update the sensor status.
  • Verify that the low battery trouble has cleared.
  • If the trouble remains, confirm that:
    • The battery is installed with the correct polarity.
    • The sensor housing is fully closed.
    • The sensor is properly seated on its mounting bracket.

Notes

  • The PROSIXCT uses one (1) CR123A 3V lithium battery.
  • A low battery condition may not clear immediately after replacement. Allow several minutes for the panel to receive the updated battery status.
  • If the low battery condition persists after replacing the battery and verifying installation, further troubleshooting may be required.


For reference, see the video below.

https://www.youtube.com/watch?v=IVZT1OTnJJc