A simple panel swap turned into a four hour nightmare because of one hidden wire

Had a job yesterday to swap out an old Vista 20p for a newer model at a house in Tempe. The homeowner said the old system was acting up, easy enough. Pulled the old panel, everything looked standard. Started wiring the new one, got to the keypad line and realized the old installer had run a single 22/4 for both power and data to the main keypad upstairs. No big deal, I can work with that. But then I found a second, completely separate 22/2 running from the panel area up into the same wall cavity, just cut and tucked back with no label. Spent the next three hours tracing it. Crawled through the attic, pulled the keypad off again, finally found it looped into a motion sensor in a closet we didn't even know was on the system. The original notes from 15 years ago were wrong. What should have been a 90 minute job took me over four hours. Anyone else ever get totally blindsided by a mystery wire that wasn't on any diagram?

3 comments

3 Comments

stella3072mo ago

Mystery wires are the worst. Read a forum post last week where a guy found a dead 18/2 just coiled in a ceiling. It was for a long gone smoke detector. No record of it anywhere. Those old install notes are basically useless after a few years. People add stuff, take stuff out, never write it down. Turns a simple swap into a full detective job. Always gotta budget double the time for those old systems.

eva_garcia562mo ago

My cousin does low voltage work and told me about a hidden wire for a panic button under a desk. It was spliced into a door contact circuit from like 1998. The prints showed nothing, took him half a day to figure out why the zone kept faulting. Old notes are a total gamble, lol.

xena_miller311mo ago

Oh man, I got one for you. Last year I was swapping out a panel in an old house in Scottsdale and found a single 22/2 tucked behind a baseboard with nothing attached to either end. Turned out it was for a tiny glass break sensor in a laundry room that had been painted over and forgotten for like a decade. The original install doc just said "motion zone 2" with no mention of it. I spent three hours in the crawlspace with a toner trying to figure out if it was still live or just dead wire. Finally cut it out and capped it, but man, that job was supposed to take two hours and ate up my whole afternoon. Old systems are like a treasure hunt nobody asked for.