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Ran a 3 day test disarming the panel with the dialer hooked up instead of pulling it, weirdest thing happened
Last week I had a service call at a dentist office in Boise where the DSC panel kept false alarming every morning around 6:45. I tried the normal stuff first, new battery, checked the door contacts, swapped a motion, nothing. On a hunch I left the dialer connected while I metered the loop instead of disconnecting the phone line like I always do, and the alarm quit tripping for 3 straight days. Ran it back with the dialer pulled and it false alarmed the next morning, so something about that tip and ring voltage was bleeding into the zone circuit. I've been doing this 11 years and nobody ever showed me that trick, my old lead just said yank the dialer first and don't touch the phone line. Now I'm wondering how many panels I've replaced over the years when the actual problem was a short on the phone side. Going back Thursday to test it with a known good dialer and see if it repeats. Has anyone run into the phone line causing zone faults on old DSC boards, or am I just chasing ghosts here?
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knight.mason2d ago
The tip and ring acting like an antenna for a floating ground makes sense, and if that old board has weak filtering on the zone input it wouldn't take much ripple to trip it at the same time every morning. You could probably prove it by running the panel off a battery alone with the dialer hooked up and watching if the fault disappears when the landline is unplugged. If it repeats Thursday, check the ground wire on the phone block too, a bad earth there would explain why it only shows up at that one spot.
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