Just realized I've been testing capacitor discharge wrong for years

I was reading through a tech manual from 1987 last night and it mentioned using a 20k ohm resistor instead of my usual screwdriver short method. Tried it this morning on a dead fridge compressor start cap in a KitchenAid and the discharge was way smoother with no spark. Has anyone else switched to resistor-based discharge and noticed less damage to the capacitor terminals?

2 comments

2 Comments

cooper.nathan19d agoMost Upvoted

Has anyone ever had a screwdriver slip and launch across the garage like I did last Tuesday? I nearly took out my good multimeter. The resistor method might be slower but at least my tools stay where I put them. Seriously though, I switched to a 15k ohm resistor after reading that old manual too and the lack of spark is comforting. Have you noticed the caps hold their charge longer with the resistor or is that just me being paranoid?

xena_jackson19d ago

Wait, are you saying the screwdriver method damaged the terminals? I mean, yeah it sparks and it looks scary but I've never actually seen it hurt the posts on a cap. Those terminals are made to handle way more than a quick short. The real issue with the screwdriver trick is you can't always be sure you got a full discharge, especially on big motor start caps that like to bounce back a little. The resistor method is cleaner for sure and I get why people like it for sensitive circuits, but for a fridge cap that's just going to sit in a box until the compressor needs replacing? I think you're overthinking it. I've been doing the screwdriver thing for over a decade on everything from microwaves to AC units and never had a terminal fail on me. Maybe once in a while on some really old crusty caps but that was probably just age anyway.