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Re: Batt. cutoff switch

Subject: Re: Batt. cutoff switch
From: Richard Welty <>
Date: Thu, 10 Feb 2000 09:49:29 -0500
there are standard ways of doing a cut off switch in a alternator equipped

the way that i used in my IT car, and recommend to others in my capacity as
a tech inspector, is to purchase the 3 pole type cutoff switch.

one pole is used to switch off the battery. another pole is used to
disconnect the low voltage side of the ignition coil. the third pole is
opposite in sense the other two -- when they are disconnected, it's purpose
is to ground the positive side of the alternator through a resistor.

if you have this setup, 1) your engine _will_ stop and 2) you will not fry
your alternator.

it is important to do this correctly; i regularly test these things when
doing annual inspections of race cars, and on several occasions the car has
kept running after the switch is turned off. normally what happens is that
the driver _thought_ the car was wired correctly, and failed to do a proper
test. in testing, it is essential to start the motor, rev it up to
3000-4000 rpms briefly to energize the alternator, and then wait a beat
before hitting the switch. if the alternator hasn't spun up, then you may
be fooled into thinking a cutoff switch works when it actually doesn't.

   NEDiv Divisional Administor, Scrutineering, SCCA

Richard Welty       
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