Stupid mistake with limit switch wiring I see all the time

Went to fix a stuck car at a 12 story building downtown last Wednesday. Another company had been there the week before and replaced the limit switch. But they wired it normally closed instead of normally open. Took me 20 minutes of scratching my head before I caught it. Why do so many guys get this backwards? It says it right on the schematic. Has anyone else run into this kind of thing where a simple wiring swap cost a whole afternoon?

3 comments

3 Comments

the_rowan28d ago

Ugh yeah that's a classic. It's like people just assume the default is closed because that's what a limit switch looks like it should do. But the whole world runs on backwards assumptions like that, not just wiring.

the_riley28d agoMost Upvoted

Got a buddy of mine who works maintenance at a hotel downtown, and he told me he spent three hours chasing a limit switch issue on a dumbwaiter. @the_rowan you're right, it's like people just see the switch and assume closed without checking the print. Turns out the last guy wired it normally open when the diagram clearly said normally closed. My buddy said he about lost it when he finally found it - a simple swap that easy, but it cost him half his shift.

julia_carter7023d ago

I see it a little different, @the_rowan. Checking the print is always the right call, but sometimes the wiring gets swapped during a repair and nobody updates the diagram. I've had times where the print was wrong and the switch was actually fine. It happens both ways.