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Posted by: alpha434 Mar 25 2007, 03:49 PM

I've got some really nice battery cutoff switches, with just the two contacts. I heard from a buddy that when you use it, inline with just the negative side of the battery (or pos, etc.) you can blow the diodes in the alternator when you disconnect. But even though he happens to be an engineer, he can't explain to me why. Or the mechanism that causes it to blow.

Can anyone tell me why I can't use these switches, or that this is indeed a real danger? Thanks!!!

Posted by: john rogers Mar 25 2007, 04:24 PM

With an alternator, you will need the extra connection module on the bottom of the kill switch that includes the big resister (I think it is) to ground so when the switch is thrown to kill the engine it will stop the engine. Otherwise the engine can continue to run on the alternator and it will burn up.

Posted by: Brando Mar 25 2007, 05:17 PM

QUOTE(john rogers @ Mar 25 2007, 03:24 PM)

Posted by: alpha434 Mar 25 2007, 06:18 PM

Brando. That was how I planned on doing it. Will that damage the system at all when the switch is thrown.

I'm not going to use it day to day. But If I'm already in a situation to use it, then I don't need any more damage to my car.

Posted by: John Mar 25 2007, 07:21 PM

It is my understanding that this will eventually destroy the alternator. The safe way is as John Rogers mentions. The main positive cable is broken by the large set of contacts. Separate contacts will shunt the alternator to ground via a load resistor.

The single pole disconnect switches are no better than disconnecting the battery with the engine running (not recommended as it will eventually destroy the alternator).

The multiple pole disconnect switches are the only safe way to wire in a kill switch.

Here is a PDF file with directions:




Attached File(s)
 Porsche_Kill_switch.pdf ( 99.17k ) Number of downloads: 180

Posted by: Aaron Cox Mar 25 2007, 11:42 PM

if you need just an ignition kill, and have an aftermarket cdi box, you can use the power lead to the BOX to kill

Posted by: alpha434 Mar 26 2007, 09:44 PM

I figured it out. Kill the power input into the coil. BAM! Dead. And there's a wire to do just that at the ignition. And the fuel pump wire too... Perfect.