14awg Romex Discoloration

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e.man91

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Have not seen this much before so wanted to join the forums to get some opinions. Opened up some drywall in a small bathroom remodel to see a less than legal splice job, and some discolored romex. The circuit is a 15amp lighting circuit. The discoloration seems to wipe off, and there doesnt seem to be any physical damage to the casing, it just seems strange where the discoloration seems to start and stop. The house is not old, roughly 15 years old. Any ideas about what could cause this? I know im going to be repairing the splice, however should the whole run be replaced?

IMG_6578-min.jpgIMG_6577-min.jpg

Thanks in advance for any suggestions!
 
If it wipes off it was probably something that got onto it before it was even installed.

In one picture the two places it is seen are about right distance apart that it could easily have been on same side of the coil or reel before unwinding it to install it.
 
If it wipes off there's little reason for concern. But what are we looking at...maybe 4 feet of NM into boxes exposed at both ends? Replace it anyway unless the splice can be landed in an existing box.
 
thanks for the suggestion! If I can easily reveal the first box I’ll just replace all of it. I guess I was just asking for future refrence. Just seemed strange that all the discoloration appeared right before and after the wire passed through a tight space. (Holes in studs, and wire staple) but in the past, heat damage has always looked different, usually a mix of brown and black with some melting damage to the casing.
 
I would not get real excited about the surface discoloration. hard to tell what it might be and if it wipes off it has not hurt the insulation any. might be black mold though. might want to take a closer look as long as you have the wall cavity open.
 
Funny.. I was thinking someone just marked it with magic marker..two of the studs sho what looks to be water getting to them but no mold signs... just the discoloration...
 
Mold crossed my mind, but it seems to only be on the cable, that is why I think whatever it is was on cable before it was installed.
 
Thanks for all the replys. To add to the mystery...

Noticed the same discoloration on an exposed 15amp arc-fault bedroom receptacle circuit. still 2 wire, so I thought possibly same roll.
Then noticed more on a 3wire in the attic, same circuit as the one pictured, with discoloration. Again both areas could be wiped clean.
The 3 wire also had some area on the wire that looked more like heat damage to me (pictured) since it has some brown around the outside. Breaker problem possibly? All the existing bathroom lighting will be replaced with LED's so there will be even less load than before, but just seems weird.

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Years ago I ran across this in a brand new 1000' roll of NM cable, I couldn't figure it out either. Then for one part of the job I had it all laid out on the floor and could see that the spacing of the mars were consistent. Guess what? They were every 10 feet! The marks were there for people wanting to count how much was being spooled off as it goes.
 
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