Took me 3 blown controllers to learn this trick about door lock circuits

I kept chasing intermittent faults on Otis 411 door lock circuits. Replaced two LCI controllers and a DSS board before I figured out the real issue. Turns out the old door lock contact screws were loose and vibrated just enough at high floor travel to break the circuit momentarily. A tiny drop of blue Loctite on each screw fixed the problem for good. No more phantom faults and the customer stopped calling me at 2 AM. Anyone else ever go crazy on a simple loose connection like this?

2 comments

2 Comments

nathan2891mo ago

My buddy Mike spent three weekends tearing apart his basement door lock system, replaced every board twice, only to find the ground wire was barely touching the screw terminal. He still brings it up every time we have a beer.

the_lucas1mo ago

Bet Mike's still grounding that story into every conversation.