Nearly fried a brand new relay board on an Otis hydro last week

I was swapping out a failed KAS relay board on an Otis 211 hydro in an old building downtown. Everything looked fine on paper, so I popped the new one in and powered it up. Within 2 seconds I smelled that horrible burning electronics smell and saw a tiny puff of smoke near the terminal block. Turns out the old board had a hidden jumper wire bridging two pins that wasn't on the schematic, and I didn't catch it beforehand. Has anyone else run into a situation where a previous mechanic left a secret jumper or mod that messed with a straightforward swap?

2 comments

2 Comments

clairebaker26d ago

Read a post on an elevator mechanic forum once where a guy found a jumper wire hidden under some tape on a KAS board. People in the comments said it's pretty common in old Otis hydros because some mechanics just work around bad traces instead of replacing the whole board. I'd check for that from now on, maybe even take a photo of the old board before you pull it out. A little bit of prep can save you from smoking a brand new part.

max_foster26d ago

Oh yeah, the jumper wire trick. I fried a board once myself cause I didn't look close enough.