School job in Phoenix made me rethink my whole testing process

I was doing a panel swap at a middle school in Phoenix last month and everything looked fine on my meter. Voltage good, continuity good, the whole nine yards. But when I powered up the new panel the communicator would not connect. Spent like 2 hours going back and forth with tech support before one of them asked me to check the RJ jack on the old alarm cable. Turns out there was a tiny break in the orange pair that only showed up under load. My meter showed continuity because the wires barely touched but once current flowed it failed. Now I test every pair with a proper line tester that puts a load on the wires before I leave a job. Has anyone else run into phantom wiring faults that only act up with a real signal going through?

2 comments

2 Comments

riverp3726d ago

That "looked fine on my meter" part hits hard. I got burned the same way on an old residential alarm system a few years back. My meter said everything was good on the wiring, but the sensors would randomly go offline at night. It turned out to be a loose screw terminal that had corroded just enough to pass a basic resistance check but would drop out with any real current. Now I always do a wiggle test on every connection while the meter is still attached, and I carry a cheap line tester for the low voltage stuff. It's amazing how many problems are caused by what looks like a perfect connection when you're just checking with a meter.

jessicamiller26d ago

Wiggle test saved me too, @riverp37.