Security & Fire Protection Systems/FBII XL 2T Battery Replacement Issue


Need Help.. My Alarm started sounding but not the usually alarm sound. I checked the panel and the AC/LB light was flashing. I did some research and read it might need a Back up battery replacement. I purchased a new battery and installed it. Once installed, the alarm beeped and AC/LB light was a solid green. After about 2-5/min the alarm started sounding again and AC/LB was again flashing yellow. Did I miss something? Also when I disconnect the battery the how system turns off while still plugged in to the wall. Your help is greatly appreciated!!!!

Check the wallwart transformer hasn't come loose from the plug.  Sounds to me like you have a power problem.  If the transformer is plugged in properly, take your voltmeter and measure across the AC input terminals (identified on the diagram inside the door).  If you don't get 12 or 14VAC, then you've got to replace the wallwart as you've probably blown the fuse.  You can only use a 12VAC rated transformer.  DO NOT attempt to use a 16VAC rated transformer.  Good luck!

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Frank Kurz


Questions relating to Burglar Alarm and Security Equipment, Fire Alarm and Extinguishment Systems, Access Control, CCTV Systems, Installation, Service, Testing, Verification


30 years installing, servicing, and testing security, access control, extinguishment, and fire alarm systems

Chair of ULC Working Groups for Fire Alarm Testing (CAN/ULC-S536) and Fire Alarm Verification (CAN/ULC-S537), Executive Director of the Fire Protection Technicians Network (

Publications, Better Business Bureau Magazine, Applied Science Technologists and Technicians of British Columbia ( SUPPRESS! and Techs Fire Break Newsletters

Associate in Science; Emergency Systems (University of British Columbia); Aircraft Maintenance Technology (BCIT)

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