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Re: Fuses

To: mgs@autox.team.net
Subject: Re: Fuses
From: Graham McCann <gmccann@pcug.org.au>
Date: Thu, 06 Jun 1996 09:49:37 +1000
At 01:06  5/6/96 +0600, you wrote:
>G.J. wrote:
>>While on the subject, What are the proper fuses for the '72 'B? ie, amps, 
>>slow blow vs fast, etc...   (Who *knows* if I have the right ones in...) 
>>What is connected to each of the four fuses?
>>
>>Of course, lets check out the manual...oh, here it is, under fuses...:
>>
>>17 amp current rated, 35 amp blow rated (same as 35 amp fast blow?)
>
>Not a bad question.  Something I've wondered about myself.  There was a
>time long ago when I went through fuses pretty quickly, exhausting what
>I thought was an adequate supply.  I've been driving with exactly one
>spare for years, but now that I've said something about it you can
>be sure I'll have a fuse blow the next time I drive the car.
>
>If I get them from the AP store, should I pick up 17 amp (close to,
>anyway) or 35 amp fuses?  The conductor in either one looks much larger
>than the regular Lucas ones.  35 amps sounds like an *awful* lot of
>current to pipe through the car's wiring.
>
>What the heck does "17 amp current rated, 35 amp blow rated" mean, anyway?
>Is it something like "it can handle 17 amps all day, 17 to 35 amps will
>slowly burn it out, above 35 amps will blow instantly"?
>--
>Jay Tilton  |  jtilton@vt.edu
>
17 Amp continuous and 35 amp blow means just that.  In other words the
requirement is 17 amps but there might be spikes of voltage for one reason
or another but that the fuse will stand that - but not a continuation of
that flow.

A 30 or 35 amp continuous fuse - such as you might buy at the local shop
will not blow at less than that rating.  In many instances the wiring in the
car is rated at less than 30 amps so a fire is inevitable.  I firmly believe
that you should use as low a rated fuse as possible.  To achieve this I fit,
say, a 15 amp fuse  and see how it goes - making sure I am carrying spares
of a higher rating if it is not up to the task.  There is no question that
the factory did not intend there to be fuses of above 17 amps continuous
fitted to MGBs,

You can buy continuous/blow rated fuses but it is easier to carry spares of,
say, 15 amps continuous and replace them if there is a voltage 'spike'.  You
probably want to know what caused the spike anyway.

regards
Graham McCann  Rivett, ACT. Australia
gmccann@pcug.org.au
06 2889055
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