Re: Cig lighter kill switch

[Norman Boehl <nboehl@xxxxxxxxxxxxxxxx>]

Hey guys,

Just to clarify the wiring for a "kill" switch that uses the
cigarette lighter as the "kill" switch, it must be noted that
the "start" signal must be switched at its source, i.e., the
ignition switch.

I have included some schematics below that will hopefully convey
the idea in a clearer fashion.

Under normal (unmodified) conditions, the "start" signal becomes
active when the ignition switch is turned to the "start" position.
It is inactive in all other positions, including the "run"
position.

To change the wiring, locate the "start" signal where it leaves
the ignition switch/steering column, and cut it.

Also, disconnect the two leads that are currently connected to
the cigarette lighter (tape them up (separately) to prevent
shorts).  These two leads will remain unused and can be stuffed
under the carpet, or used as an accessory connection, etc.

Make new connections as detailed below.

   1)  Connect the "hot" side of the "start" signal lead
       (the wire that you just cut) to one of the cigarette
       lighter terminals.

       Splice another wire at this connection and connect the
       other end to one terminal of the normally open relay
       outputs.

   2)  Connect another wire to the remaining terminal of the
       cigarette lighter, and connect the other end of this
       wire to one of the terminals of the relay inputs.

   3)  Connect the remaining "start" signal lead (the wire that
       you just cut) to the remaining terminal of the normally
       open relay outputs.

   4)  Connect the remaining relay input terminal to ground.

When the wiring is modified as per the schematic, the "start"
signal actually "switches" itself via the cigarette lighter
and the normally open relay.  If the cigarette lighter is not
pushed in, the "start" signal is left open via the normally
open contacts of the relay.  When the cigarette lighter is
pushed in, the relay closes the contacts, thus routing the
"start" signal as in the unmodified circuit.

Note that power is applied to the relay only when the ignition
switch is turned to the "start" position.  Thus, no current drain
under driving/parked conditions.  You can leave the cigarette
lighted in its "out" position at all times except when you want
to start the car.

Hope this helps,
Norm


NORMAL WIRING
=============

          /
         /       "start"
+12V ---o    o---------------------------------------------------> "start"
                    ^
       IGNITION     |
       "START"      +-- cut here
       POSITION


MODIFIED WIRING
===============
                                       RELAY (N.O.)
          /                 /         +------------+
         /       "start"   /          |            |
+12V ---o    o------o-----o   o----------o      o----------------> "start"
                ^   |                 |            |
       IGNITION |   |    CIGARETTE    | IN     OUT |
       "START"  |   |     LIGHTER     |            |
       POSITION |   |              +-----o      o--------+
                /   |              |  |            |     |
               /    |              |  +------------+     |
        "hot" /     |              |                     |
        side        |              |                     |
                    +--------------|---------------------+
                                   |
                                   V
                                  gnd


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