Intermittent electrical faults

Whilst working on my build at the weekend I came across a classic example of something mentioned in my "fault finding guide". When it comes to tracing broken wires it is often possible to pin-point as the wire bends in an unnatural way - that is to say that when you bend it rather than following a uniform radius the wire actually "folds" at the point where the core has failed. You can see this in the below pic where on the left the break is !! In this case the cable actually feels "limp" at the broken point.

Is this a "single core" cable, or an original-Kawa- multi-copper-wire"-cable?
However, a case like the one you’ve shown here tends to occur more often with single-core, "stiff" cables—those with a solid core.
Such internal breaks are relatively rare in multi-strand cables, which are significantly more flexible and can withstand more bending....Right?   

MFP-Joe wrote:

Is this a "single core" cable, or an original-Kawa- multi-copper-wire"-cable?
However, a case like the one you’ve shown here tends to occur more often with single-core, "stiff" cables—those with a solid core.
Such internal breaks are relatively rare in multi-strand cables, which are significantly more flexible and can withstand more bending....Right?   

This is the OEM oil pressure switch wire (single core is almost never used in automotive applications) this is often the result of compromised insulation allowing moisture to penetrate and rot the core. I had the same thing with an ABS sensor wire on my 5 year old Jaguar !!!!

   That's a very good visual example of what a break of a stranded (or solid) conductor inside otherwise sound (looking) insulation looks like.  We've seen it a few times in stranded conductors within insulation of wiring harnesses where they flex repeatedly at the steering head.  Too, it's a timely issue right now at an automotive forum slmjim sometimes haunts.

   Ah, the joys of the intermittent electrical fail; a hated bane of any hardware Tech.

   slmjim was a photocopier Field Tech for years early in his work life.  Even if a later digital machine threw a code, it was sometimes unhelpful at best, a red herring at worst.  Earlier analog machines couldn't generate codes at all.
   Low-info office workers would get bent because off course, it was "my fault" the copier would intermittently misbehave.  "Don't you know what you're doing?", was a comment sometimes heard on subsequent visits for the same problem.  Throwing pricy parts at it at customers' expense is not an option, especially at $130.00 / hr. plus travel time for outlying areas.
    Best explanation I was ever able to come up with is:
   "An intermittent failure that can't be replicated at will is, by definition, the most difficult to find.  A Tech never knows if that last diagnosis & repair attempt really fixed it, or, if the failure has just intermittently disappeared again, until an indefinite period of time has elapsed."
   Even some cube dwellers / pencil pushes / bean counters / and those pretty welcome desk girls with low blouses and deep clevo could often reluctantly understand.

Good Ridin'
slmjim & Z1BEBE

I’m familiar with this kind of wiring issue—especially on our Kawasakis—particularly where there are multiple soldered connections (like at the main junction box behind the colored connectors). Over time, the solder joints can corrode, leading to sudden increases in electrical resistance and heat buildup.

However, the kind of example Wookie58 showed could also a result from someone having pierced the wire with a sharp-tipped test probelight, allowing moisture to constantly seep in through the damaged insulation.

Yeah, I "love" these kinds of wiring and electrical problems too—always exciting and time-consuming...At its best at night, in a rainy thunderstorm on the road,..have had that kind back in the early 80`s on my `73 Z1:
A short somewhere in the backlight-cable that runs trought the rear fender,..had made it "all lights and ign-out" with that "one-breaker-circuit "on the ol`Z1 electric..
I didn't discover the exact fault—or where it was located—until the next day; after testing various circuits to see which one might be affected and finally using up my last spare fuse, I drove home in that dramatic, rain-soaked darkness with *no* lights... I’ll never forget that horror-trip on the autobahn...