Almost every BMW E39 (5-series) and E38 (7-series) and E46 (3-series)
has shorts that develop in the trunk wiring loom - all in the same spot!
Here is a picture of the uniformity of the shorts:
Here is another picture from another vehicle:
I could go on (and on); but we can't figure out WHAT the BMW design flaw is.
Q: Can you tell from these pictures what the BMW design flaw is?
yeah, it's easy.
1. the wire coating has a poor grade of plasticizer*, so the coating
cracks and bending concentrated at the cracked coating will fatigue the
2. they're using an elbow bend, not a torsion bend. the stress
concentration at the surface of the wire coating is less with a torsion
#1 is a factor of the germans being too "green" for their own good and
not using good old toxic pvc. #2 is the real screw-up - they would know
that one if they'd spoken to anyone who'd been around the block or had
done their own testing.
* the plasticizer used in the wire coating is crucial to give it
flexibility. the basic polymer insulator extruded over the wire is very
brittle without it, so a plasticizer is added for flexibility. if the
plasticizer is too volatile and evaporates over time, the coating will
become hard and brittle per the original polymer, then crack when
bending stress exceeds a certain value.
i think that was back when they were using lead pigments - hasn't been
for a while now fwiu. and lead is a no-no here too.
besides, pvc isn't exactly healthy - i think they now use something
called "epdm". with the right q.c. and testing, there's no reason that
insulation should have degraded, and with the right physical layout, no
reason it should have been challenged even if it did.
And maybe you've found the root cause of the problem.
Instead of using decent wire suited to the application,
the Europeans chose to use some green hippie wire,
that not only costs more, but fails.....
respectfully and completely disagree on that. the stranding is
perfectly fine if the insulation remains intact. once the insulation
cracks, then you have substantial strain concentrated in just one spot.
even fine wire high count stranding will break if subject to such a
the fix is both better wire insulation that doesn't become brittle, AND
re-routing to avoid the elbow bend. then you can keep using cheap wire
and don't need to spend money on the expensive hi-flex stuff.
my wife broke the inside passenger side..
i've learned to use only two fingers to pull on the handles, don't
i agree they are not very rugged...
but it's about the only flaw i've found with that car (knock knock)
besides the rear door wires which i understand like the BMW is a very
common spot for wires to break on this car...
and interestingly the rear door is used maybe 1/100 of the time
compared to the drivers door so you would have to think there is
something "special" about the way those particular wires are designed
and/or built to make them break before the drivers door wires break
The inside handles seem to be designed to break at the 8 to 10 year
mark. The have a slot molded in to the highest stress point, I might add
I don't see any reason for it. Other than to help the dealer sell
Other than the door handles I'm a happy Toyota owner, had a Camry,
have a T-100 still a sharp looking truck, have a Lexus and an Avalon.
My wife is a persistent patient shopper, and will wait until she finds
a great used car at a steal.
Of course it can be. If BMW uses some hippie green
insulation that isn't as pliable as other insulation, then
the insulation will crack. We can't do a forensic investigation
from some pics that don't show how it's mounted, how
much it moves, what tensions are on it, etc. But I'd bet
that area has more bending, tension, etc than the rest of
On 03/14/2013 01:11 PM, email@example.com wrote:
Yes, that much is true. Someone had mentioned that having the wire in
that area flex in torsion would be preferable and I agree with that
statement as well. Would be simple to have accomplished by having the
hole in the body offset by a few inches (actually as far as possible
would be preferable) from the hole in the trunk lid, and using a
correspondingly longer rubber boot. then most of the flexing of the
wire as the trunk lid opens and closes would result in a slight twisting
of the wire rather than a sharp bending.
The same holds true for wiring running from a body pillar into a door
e.g. for power mirrors, windows, speakers, etc.
replace "roosters" with "cox" to reply.
I have seen a lot of cars over the years, and I have never, ever seen one
that used anything approaching quality wire.
And that begins with the '72 Datsun I had, where all of the insulation turned
to goo and every foot of wire in the body had to be pulled out and replaced.
Just take a look at what goes into airplanes vs. what goes into cars and
you'll be staggered.
"C'est un Nagra. C'est suisse, et tres, tres precis."
you're spoiled if you work on aero-spec stuff.
car quality goes in cycles - for some manufacturers anyway. in the late
80's, hondas used a higher grade under the hood - fine wire high count
high temp high flex [though not silicone], and it's remarkably reliable.
in the mid 90's they changed to lower flex, smaller cross-section,
lower count, much more akin to the wire used in the rest of the vehicle
- it still just about hangs in there, though i doubt it's million mile
material. i'm pretty sure copper prices had a big influence on this.
Did they tin it? The lack of tinning is one of the things that annoys me
about many of the cars of that era.
Silicone is actually a problem for cars because if you nick the insulation
the cut will propagate until it becomes a break.
It wasn't failing enough, so they had to downgrade it.
"C'est un Nagra. C'est suisse, et tres, tres precis."
no, it's not tinned.
there are two schools of thought on that. on the one hand, surface
oxidation resistance is a good thing. on the other, there may be a
problem with tin in fatigue environments. i don't know this for sure,
so if you know someone at work who does, it would be good to check - but
tin has a weird deformation mechanism called "twinning" which changes
the surface of the metal where it's occurred. given that almost all
fatigue initiates at a surface, that /might/ be a fatigue initiator.
how much it might be worse than oxidation, i can't say, but i know a lot
of mil spec wire is silver plated, not tin, so i think it might not be
simple cheapness preventing its use.
indeed, but that's not unique to silicone - many elastomers have the
maybe. it was was bullet proof - never failed unless abused.
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