A few years back I self installed a system based on a ADEMCO 40P panel.
Everything has been working fine until recently, when the system was powered down for a few hours.
It came back uo OK, functional and with all programming apparently intact, except that now every night about 1:00AM I get an alarm and the error message "comm error". Very annoying!
This system is not and has never been wired to any sort of communications line or device.
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Try going into program mode, and then out again. This will reset the system, without powering it down. Somewhere in programming you may also have something set to transmit troubles, which is what it is trying to do. Or, if it happens at the same time every day, it could be set to send a test signal on a 24 hr. interval, which is at 1:00AM, and when it fails, it trips the comm error. Check your programming fields.