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Re: [TR] TR2-3 electrical melt downs

To: DAVID MASSEY <dave1massey@cs.com>
Subject: Re: [TR] TR2-3 electrical melt downs
From: bill beecher <notakitcar@yahoo.com>
Date: Wed, 24 Jun 2020 09:52:28 -0500
Cc: "triumphs@autox.team.net" <triumphs@autox.team.net>, "fot@autox.team.net" <fot@autox.team.net>
Delivered-to: mharc@autox.team.net
Delivered-to: triumphs@autox.team.net
References: <35829924.2130934.1593009476585@mail.yahoo.com>
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I counted, I only have two(2) fuses on my =E2=80=9858 TR3.   Where might the=
 other be?
Thx,
Bill B
TS30800L

Serenity Now......

On Jun 24, 2020, at 9:38 AM, DAVID MASSEY <dave1massey@cs.com> wrote:

=EF=BB=BF
Keep in mind that these wire harnesses, like the car as a whole, was designe=
d to a budget.  These harnesses had three (count 'em, 3) fuses.  As such som=
e items were unfused like the headlamps and the coil.  And those things that=
 are fused shared a fuse so the fuse had to be sized to carry the current fo=
r everything on that circuit.  But the wires were sized for the particular l=
oad.  A thinner wire will have a nigher resistance and under  short-circuit c=
onditions the current can be limited to a level that will not blow the fuse b=
ut the current will cause enough heating to cause the insulation to melt.

Another factor against us is the age of the harness.  The connector contacts=
 get corroded and will get hot under normal circumstances.  Wire strands can=
 fatigue and break within the insulation again resulting in overheating unde=
r normal use.  The insulation gets stiff and cracks exposing the wires withi=
n.  Lots of potential failure modes here. =20

Compare this design to those found in modern cars you will see dozens of fus=
es.  Sure there are a lot more electrical items but most things have their o=
wn fuses.  This means you can size the fuse more appropriately for the wire u=
sed to power that device.  Also the connectors used are water tight and don'=
t corrode as quickly.  Also, they are, on the whole, a lot younger and there=
fore retain more of their original integrety.

But a fresh works well enough so if you fear a melt-down a new harness may b=
e a good investment.

Dave=20



-----Original Message-----
From: bill beecher <notakitcar@yahoo.com>
To: Tom Householder <trhouse@columbus.rr.com>
Cc: Triumphs@Autox.team.net daily digest <triumphs@autox.team.net>; FOT List=
 <fot@autox.team.net>
Sent: Tue, Jun 23, 2020 8:52 am
Subject: Re: [TR] TR2-3 electrical melt downs

Have a friend with a TR6 that had a significant meltdown behind the dash.  I=
 should think, given the right set of weaknesses, most any section could mel=
t.=20
Bill B

Serenity Now......

On Jun 23, 2020, at 4:52 AM, Tom Householder <trhouse@columbus.rr.com> wrote=
:

=EF=BB=BFOver the years I have experienced and seen harness melt down in the=
 looms to the tail lights .. anyone ever had an under dash melt down?

Trying to answer a question asked of me.=20

Tom=20
** triumphs@autox.team.net **

Archive: http://www.team.net/pipermail/triumphs http://www.team.net/archive

r@yahoo.com


** triumphs@autox.team.net **

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ey@cs.com

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<html><head><meta http-equiv=3D"content-type" content=3D"text/html; charset=3D=
utf-8"></head><body dir=3D"auto">I counted, I only have two(2) fuses on my =E2=
=80=9858 TR3. &nbsp; Where might the other be?<div>Thx,</div><div>Bill B</di=
v><div>TS30800L<br><br><div dir=3D"ltr">Serenity Now......</div><div dir=3D"=
ltr"><br>On Jun 24, 2020, at 9:38 AM, DAVID MASSEY &lt;dave1massey@cs.com&gt=
; wrote:<br><br></div><div dir=3D"ltr">=EF=BB=BF
<div style=3D"color:black;font: 12pt Arial, Helvetica, sans-serif;">
<div> <font size=3D"3">Keep in mind that these wire harnesses, like the car a=
s a whole, was designed to a budget.&nbsp; These harnesses had three (count '=
em, 3) fuses.&nbsp; As such some items were unfused like the headlamps and t=
he coil.&nbsp; And those things that are fused shared a fuse so the fuse had=
 to be sized to carry the current for everything on that circuit.&nbsp; But t=
he wires were sized for the particular load.&nbsp; A thinner wire will have a=
 nigher resistance and under&nbsp; short-circuit conditions the current can b=
e limited to a level that will not blow the fuse but the current will cause e=
nough heating to cause the insulation to melt.</font></div>

<div><font size=3D"3"><br>
</font></div>

<div><font size=3D"3">Another factor against us is the age of the harness.&n=
bsp; The connector contacts get corroded and will get hot under normal circu=
mstances.&nbsp; Wire strands can fatigue and break within the insulation aga=
in resulting in overheating under normal use.&nbsp; The insulation gets stif=
f and cracks exposing the wires within.&nbsp; Lots of potential failure mode=
s here.&nbsp; <br>
</font></div>

<div><font size=3D"3"><br>
</font></div>

<div><font size=3D"3">Compare this design to those found in modern cars you w=
ill see dozens of fuses.&nbsp; Sure there are a lot more electrical items bu=
t most things have their own fuses.&nbsp; This means you can size the fuse m=
ore appropriately for the wire used to power that device.&nbsp; Also the con=
nectors used are water tight and don't corrode as quickly.&nbsp; Also, they a=
re, on the whole, a lot younger and therefore retain more of their original i=
ntegrety.</font></div>

<div><br>
</div>

<div><font size=3D"3">But a fresh works well enough so if you fear a melt-do=
wn a new harness may be a good investment.</font><br>
</div>

<div> <br>
</div>

<div style=3D"clear:both"><font size=3D"4">Dave </font><br>
<br>
</div>

<div> <br>
</div>

<div> <br>
</div>

<div style=3D"font-family:arial,helvetica;font-size:10pt;color:black">-----O=
riginal Message-----<br>
From: bill beecher &lt;notakitcar@yahoo.com&gt;<br>
To: Tom Householder &lt;trhouse@columbus.rr.com&gt;<br>
Cc: Triumphs@Autox.team.net daily digest &lt;triumphs@autox.team.net&gt;; FO=
T List &lt;fot@autox.team.net&gt;<br>
Sent: Tue, Jun 23, 2020 8:52 am<br>
Subject: Re: [TR] TR2-3 electrical melt downs<br>
<br>

<div dir=3D"ltr">Have a friend with a TR6 that had a significant meltdown be=
hind the dash.&nbsp; I should think, given the right set of weaknesses, most=
 any section could melt. <br clear=3D"none">Bill B<br clear=3D"none"><br cle=
ar=3D"none">Serenity Now......<br clear=3D"none"><br clear=3D"none">On Jun 2=
3, 2020, at 4:52 AM, Tom Householder &lt;<a shape=3D"rect" ymailto=3D"mailto=
:trhouse@columbus.rr.com" href=3D"mailto:trhouse@columbus.rr.com";>trhouse@co=
lumbus.rr.com</a>&gt; wrote:<br clear=3D"none"><br clear=3D"none">=EF=BB=BFO=
ver the years I have experienced and seen harness melt down in the looms to t=
he tail lights .. anyone ever had an under dash melt down?<br clear=3D"none"=
><br clear=3D"none">Trying to answer a question asked of me. <br clear=3D"no=
ne"><br clear=3D"none">Tom <br clear=3D"none">** <a shape=3D"rect" ymailto=3D=
"mailto:triumphs@autox.team.net"; href=3D"mailto:triumphs@autox.team.net";>tri=
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