The kill switch in my car, soon to be Mark's car, is in the battery ground
circuit only. The car has a generator. The kill switch does not kill the
engine. This is because the generator will still put out voltage and current
to run the engine.
If you open the field circuit of an alternator or generator (the wire that
runs from the voltage regulator to the field, stationary in a generator and
the rotor in an alternator), it will cease to produce voltage. A generator
will still produce about 2 Volts due to residual magnetism, but this
shouldn't be a problem. This is how we turn on or off the generator or
alternator in an airplane. And "never" had a problem with it. But the alt or
gen has a separate voltage regulator, with an external wire to the alt or
gen. This wire runs through a switch in the cockpit called the alt or gen
master switch.
A certain flight instructor used to simulate an electrical system failure to
the student by pulling the circuit breaker in the alternator output, till
this fried the alternator. After that, he simulated electrical system
failure by opening the alternator master and battery master.
I think that the reason a kill switch in a racecar damages an alternator is
because the kill switch has been placed in the output circuit, not the field
circuit. "They" always say never to run an alternator without a load on the
output because it will hurt the alternator.
Most alternators used in cars have an internal voltage regulator (called a
"single-wire" alternator because there is no external field connection),
therefore the field circuit is internal to the case and this makes putting a
switch in the field circuit difficult. So they put the kill switch in the
output circuit. This will stop alternator output, but may damage the
alternator.
Couldn't you open up a "single-wire" alternator, cut the field wire (runs
from the voltage regulator to one brush), solder a wire to each end and
connect them to the unused pole on the kill switch? Then the kill switch
would stop alternator output by opening the field circuit like in an
airplane, and won't hurt the alternator. And take away battery ground with
the other pole.
Just a thought.
Dr. John Herrera
Chief Boffin
High Speed Triumph Research Laboratory, Soggy Bottom Facility
>From: WEmery7451@aol.com
>Reply-To: WEmery7451@aol.com
>To: henry@henryfrye.com, fot@autox.team.net
>Subject: Re: Kill Switches
>Date: Sun, 24 Apr 2005 23:10:00 EDT
>
>In a message dated 4/23/05 9:13:16 PM Pacific Daylight Time,
>henry@henryfrye.com writes:
>
><< My kill switch just shuts off the ground. No fancy kill switch with
> alternator contacts here.>>
>
>Breaking the ground would stop the car with a generator. If I thought
>about
>it, I could shut off the generator before the test. I wired the field
>through
>one of the stock TR pull out switches on the dash.
>
>I was thinking about doing the same thing with the one wire alternator, but
>these switches may not be able to carry the higher current. Does anyone
>know
>of a heavier duty switch like this? I have one for the ignition switch,
>which
>I took out of a junker. I can't seem to find these switches in any auto
>parts
>store.
>
>I believe that I found why my engine ran away. One of the floats had some
>gasoline in it allowing fuel to leak through into the engine. I replaced
>it
>with another old original float. I assume that the after-market floats are
>still
>no good?
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