So I am running with the SCCA now and I need to install a master kill switch to shut off the car and it's electrical system in an emergency.

I have a high current moroso switch that is single pole, single throw on / off that I will mount to the roll cage soon.

I can interrupt the #3 cable from the battery to the fuse box, but how do I disable the alternator too? That way when the switch is off the alternator output will be disabled as well, so the motor does not keep running.

Maybe run the alternator output wire to the switch as well?

 

An alternator will not keep generating power without a power source. A generator will. Old cars have generators, modern have alternator.if you kill the battery source the whole car will die in a modern car. This is not the case in a old car with a generator, or magneto. If you cut their power they continue to run.

 

bigger issue with a master cutoff on a r53 is the car has 2 + battery cables.....but it is usually considered OK to put the master cutoff on the cable going to the fusebox.....
the 2nd cable goes to the starter, and is unfused....but it is protected by the squib that disconnects BOTH cables if the airbags are deployed.....
know what you are thinking...so i will step back and say i have never installed a cutoff...but if you kill power to the ECU, the car will stop....so simpler killing an alternator....so maybe a switch on a relay tied to the master....

 

My '55 chevy drag car would keep running when I disconnected the battery, simply because the field in the alternator was exciting itself, which is why I think I will run the alt wire to the cutoff.
between that and the one to the main fuse box I should be covered, as the power to the coils and ECM will be turned off when the switch is open....

 

It's important his switch stops the engine AND the electric fuel pump in case of an accident. I would want the switch to also disconnect the electric power steering pump as well.

I think his plan would work. Including a relay for the alternator would also work. Or getting a multi-pole switch to include the alternator. Perhaps I'm reading the comment incorrectly, but switching just the alternator is not sufficient.

 

I ran a simple test....I ran the car at idle. Then I loosened the screw holding down the lug for the fusebox. The engine, and fuel pump and PS all stopped, so if I interrupt the #2 gage fusebox wire on the driver side, we will be good.

thanks for all your input. I ain't gunna win at racing, but I will be out there on a weekend bangin' gears with the best of them, with a big *** smile.

 

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