Got called out for using a multimeter wrong on a Citation 560XL yesterday

Honestly, I've been doing avionics for 7 years and I always used the continuity beep to check wiring. An older tech showed me I was getting false readings because I wasn't isolating the circuit properly. He walked me through why you gotta use resistance mode with the circuit dead and disconnected. Has anyone else had to unlearn bad habits they picked up early in the trade?

2 comments

2 Comments

taylor1743d ago

The continuity beep got me too when I first started out... it's so easy to just trust that tone and move on. What finally clicked for me was when I had a short on a Cirrus that kept coming and going with temp changes. I was chasing my tail for two days before a senior guy made me walk through the whole circuit with a schematic and a meter set to ohms. He showed me how a simple resistor in parallel with a winding was tricking the beeper into thinking there was a dead short. Now I always kill the power, disconnect both ends, and use the resistance scale to actually see the number... saved me hours on a G1000 pitot heat issue last month. It's humbling but that's how we learn in this trade.

avery_foster313d ago

Same thing happened to me about 4 years ago on a King Air 200. @taylor174 I was chasing a weird flap indication and kept getting continuity on the beeper between two pins that shouldn't have been connected. Spent half a day before a old timer came over, laughed, and made me set the meter to 200 ohms. Showed me there was 47 ohms between them from a relay coil in the circuit. Beeper just sees anything under 100 ohms as solid contact. Now I disconnect everything and use resistance mode on every check. That little number on the screen tells you way more than a tone ever will.