PSA: Found out my resistor values were drifting after 2 years in the field

I replaced an old panel at a house in Phoenix last week and checked the resistors on the sensors before swapping. Three of them were reading way off, like 30% higher than stamped. Never thought to check that before, just assumed they stayed accurate. Anyone else run into this on older installs?

2 comments

2 Comments

aarons361mo agoMost Upvoted

Dave from my firehouse crew redid his whole home system about six months back. He pulled an old panel from a house built in the late 90s and tested every resistor on each sensor before tossing them. He told me four of them were reading 25 to 40 percent higher than what was stamped on them. He said he would have never guessed they drifted that much after sitting in a wall for over a decade. I've been double checking old parts ever since he told me that story.

the_anna1mo ago

Wait, aren't those resistors usually like 5% or 10% tolerance parts anyway? 25-40% drift seems way high even for cheap ones unless they got all corroded or something.