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Re: electrical question

To: datsun_sports <datsun_sports@hotmail.com>
Subject: Re: electrical question
From: Tom Hendricksen <tom@fransfancies.com>
Date: Thu, 16 Jan 2003 20:41:00 -0800
Mike,

Did you check the fuse with an Ohmmeter or voltmeter?  The voltage should be
about the same on both sides of the fuse holder.  What is the current rating of
the fuse you installed?  Should it be larger to handle the steady load?

Fuses do not immediately blow when their current rating is exceeded.  In fact I
have measured surge currents of 200 Amps that did not blow a 1/2 Amp fuse as 
long
at the surge time was very short.  Fuses blow when the temperature of the wire
finally reaches a point at which the weakest point of the wire melts and
separates.  If you are right on the edge of the maximum current rating for the
fuse it could take a while to build up the required temperature to melt the
wire.  I have seen many fuses where the internal wire is open, but you cannot 
see
it with your eyes because the open point is right at the end cap if this is a
round glass fuse.  You must measure them with an Ohmmeter.  I found fuse
performance curves very interesting the first time I ever saw one because they
can take much more abuse than you would expect..

What kind of fuse holder are you using here?  Is it clean?  Is it rated for the
amount of current you are passing through it?  If the contact is poor you will
build up heat in the resistance between the holder contacts and the metal ends 
of
the fuse.

Tom
69 2000
Portland



datsun_sports wrote:

> hi all,
>
> i let my 67 1600 run for awhile and then checked the spliced in fuse (it is
> in place of the ammeter). it was hot and the instruments stopped working. i
> turned the car off and let it cool down. now the car does not start. the
> instruments are not working as well. all the fuses look fine. ideas?
>
> thx,
>
> mike

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