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Re: Alternators and Master Cutout Switches

To: "Steve Benford Jr." <sbracing@execpc.com>, fot@autox.team.net
Subject: Re: Alternators and Master Cutout Switches
From: Tony Drews <tony@tonydrews.com>
Date: Wed, 07 May 2003 20:07:13 -0500
I'm going to offer a little different discussion on this issue.  I've got a 
kill switch with alternator contacts.  I've used it to shut off the motor 
exactly once - to verify it worked right.  I always shut down the motor 
with the ignition switch on the dash, and then turn off the kill switch 
later to ensure that all of the accessories are off.  The one time I tried 
this I didn't blow up my one wire alternator.  I suspect that if you don't 
make a habit of using the kill switch to shut off the motor your alternator 
can have a fairly long life (unless you are Irv).  :)

I've been asked by tech inspectors if the kill switch stops the motor but 
never asked to prove it.  Proving that it works is the only reason I can 
think of actually using the kill switch to turn off the motor (other than 
the obvious "on track incident").  The tech inspector usually makes sure 
that the brake lights work with the kill switch on and don't work with the 
kill switch off.

If you are worried about the voltage spike causing an issue with the 
alternator, you can get the kill switch that switches the ignition 
separately instead.  That's what uncle jack runs.  The drawback with this 
setup is that the alternator needs to be connected to the battery side of 
the kill switch to avoid the voltage spike when disconnected.  This means 
that the wire running to the alternator under the hood is always 
hot.  Hitting that terminal with a wrench while, say, pulling the head can 
cause you to hit YOUR head on the hood.

- Tony Drews

At 07:38 AM 5/7/2003, Steve Benford Jr. wrote:
>Amici:
>
>Is it possible to wire in a master cutout switch that will shut down
>the electrical power completely?  I know there are master cutout
>switches designed for use with alternators.  How are these wired into
>the system?  My first attempt at a wiring diagram will have the car
>still running but not charging the battery when the master is turned
>off.
>
>I have heard that if the wired incorrectly, shuting down power at the
>master will cause a power spike from the alternator and fry all of the
>sensitive components in the alternator and electronic ignition.  Sort
>of like removing a connection from the battery when the car is running -
>  which is suppose to be a big no-no on modern day autos.
>
>Thanks and Thumbs Up
>Steve Benford Jr.

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