Help help, installed kill switch

[Lenie]

Bingo, thanks Ned.

[ErikLS2]

I'm late to the party as usual here but it doesn't remove the "load" from the switch to have it on the ground side, it just removes the voltage from it as the "load" in the circuit (bulb, starter, computer, etc.) uses up the voltage before it gets there. Amperage though is the same throughout the circuit, power or ground side. Most vehicle manufacturers place switches on the ground side as the lower voltage reduces the very minor arcing across the contact points (where there isn't a transistor these days) caused by the additional voltage going through it and in theory making the switch last longer.

If removing the kill switch didn't solve the problem check for voltage loss across all the wires in the circuit. This is important, do it with the circuit operating. Set your meter to volts and connect it to each end of any wire you want to check. In your case each end of each black and red wire as well as across the kill switch contacts and alternator wire. On the large gauge wires going to the starter you'll have to disable the ignition system and measure it while cranking. I would pay special attention to the wire from the alternator (it might be too small for that span) and on this one the engine will have to be running, if it will run, if not while cranking will have to do. You should read very little voltage in any of these test, not more than 0.1-0.2 volts is ideal, if more than say a volt there's way too much resistance in the circuit or the wire is too small in diameter.

[DRJDVM's '69]

KISS...keep it simple stupid..

So then the debate comes back to, which side to run the switch.... my understanding is that it really depends on what your goal is.

If the goal is to cut all power in the event of a crash etc, so none of the electrical systems have juice flowing through them, then it should be close to the BAT and on the positive side. If you crash and things are all mangled, you may have created new ground points all over the place with shorted wires...and you don't want a bunch of hot circuits anymore

If the goal is more to be able to just essentially disconnect your BAT when the car is sitting, so the BAT does constantly get drained, then just put it on the NEG side

[waynieZ]

As for the negative being switched, couldn't the starter get a dead short and cause a fire if it the positive was hot ??

[Lenie]

Disconnected from kill switch straight to battery, nothing. Decided to rewire back to original set up straight from 1 wire alternator to starter, still nothing. I believe I've done something to fry my msd 6al 6420 ignition box (must of spiked it)...no fuse..really...crap. Guess I'll buy another....hmmm cars

[waynieZ]

What would Greg Weld say That's hot rodding! Still hurts though doesn't it.
I hope you get it figured out.

[Lenie]

Originally Posted by waynieZ

What would Greg Weld say That's hot rodding! Still hurts though doesn't it.
I hope you get it figured out.

Ya just like Greg, trying to make this hobby fun!

[Lenie]

Took the long road there but got er' fixed!

[intocarss]

Originally Posted by DRJDVM's '69

KISS...keep it simple stupid..

So then the debate comes back to, which side to run the switch.... my understanding is that it really depends on what your goal is.

If the goal is to cut all power in the event of a crash etc, so none of the electrical systems have juice flowing through them, then it should be close to the BAT and on the positive side. If you crash and things are all mangled, you may have created new ground points all over the place with shorted wires...and you don't want a bunch of hot circuits anymore

If the goal is more to be able to just essentially disconnect your BAT when the car is sitting, so the BAT does constantly get drained, then just put it on the NEG side

^^^THIS^^^^

[Che70velle]

I'm failing to follow the logic of a couple posts here.
If I put my cutoff switch on the power side of the battery, it will absolutely see all the load that the vehicle is using. The power side, or positive side of the battery's circuit produces, or sees, the load. Lets say I'm using a cutoff switch rated for 50 amps, and my vehicle's electronics need more than the switch is rated for. The switch will eventually overheat and fail. Doesn't matter if you've rated the cables correctly, the switch will be the weak link. Ok, let's look at it from another view. Even if the switch is overrated for the vehicles load demands, and there is an accident that produces a short on the positive side of the battery, the switch will be the weak leak and fail. That's a good thing, as long sat the switch can be closed quickly, but what if it overheats and sticks closed, meaning you cannot open the switch? Not good. If the ground side of the circuit sees as much load as the power side, then why not fuse the grounds, and not the hot side? The ground side will see the voltage, but not the amperage, because the amperage is used by whatever is pulling it. You cannot push electricity. It has to be pulled.
So what if I place the switch on the negative side of the battery? First off, it does not see a load, and will never fail from overloading, and best of all if you remove the ground from the vehicle by switching the negative cable off, then there is never a chance of circuits becoming energized if the switch is off, meaning no "juice" can flow through them, because electricity has to have a ground, or you don't have electricity to start with. I've wired many race cars, and street cars, with cutoff switches, and believe me your taking an unnecessary risk by putting the master cutoff switch on the positive side. Will it work? Sure. Play it safe, and switch the negative side. No ground equals no power.
Did I tell you guys that I make a pretty good living messing with electricity?