I just ordered a "kill switch" since my track tech has warned me that I will need one, eventually. It is Morosso 74101 "for cars with alternators". Battery is in the trunk, so which wire(s) from the alternator do I need to run to the back for the switch to kill the alternator. Rick Book encouraged me to run a second wire from the hot terminal to the dash area with inline fuse for stereo memory (even though he uses his for computer memory to run his EFI).
i run a 1 wire alternator. 1 battery cable from the + to the switch and another from the switch to the solenoid. the alternator wire goes to the same side of the switch that goes to the alternator. i'm sure some do it other ways. this works for me.
When the tech guys says "next time you come to the track, wear long pants, shoes, and have a kill switch", that is about the time... no more cargo shorts and sandals, and the engine needs to die at the push (or turn) of a button. He has never said anything about the cooler of beer in the back seat But honestly, that is for the wife, and for me after I do my runs. 2 beers, max, then hang out a while and drive home.
I am sure the is an e.t. limit when it is required....but I was always told if the battery is in the trunk, must have a disconnect.
no et limit at all. nhra regs state you must have a kill switch if the battery has been relocated to the trunk.
Just put the switch in the ( - ) battery cable. Remember, everything that goes out has to come back in too. It won't corrode like the + side does either and you wont' have to worry about shorting anything across the posts. It'll be more simple than re-wirring everything using the switch post as the main hot. If the tech won't allow it, then you can go through the hassle of running all the hot wires through the switch. You should just be able to demonstrate that it works by killing the engine while it's idling. It's always a good idea to have a kill switch for safety reasons. I've heard of more than one car idling through the pits on fire because the driver didn't kill it before he bailed out. It's also good for electric fuel pumps. Mech pumps shut off when you wreck and kill the engine. The electric pumps keep feeding the fire.
just want to make sure that i dont have to hack one into my mostly stock car just to run the strip once or twice a year if that.definately a good safety feature that i would install on a "drag car".
it needs to be on the hot side! kinda defeats the purpose of the kill switch... if the power line hits anything during an accident... and grounds you will have a HOT wire! big no no!
Absolutly, would be like putting a shut-off valve in the drain of the sink. Will stop the flow of water down the drain but unless you shut the valve in the pressure line or faucet, you end up with free flowing liquid up to your kiester. Same goes for current flow/voltage/amperage. Must admit that I did have one in the - line on my first race car. Learned real fast about that little dumba** mistake. Fire extinguisher did it's job though, oh yeah, after the rewire to + side, did put in two extinguishers for peace of mind. No, they were not the brass pump handle one's, those were banned the year before.
The switch needs to placed at the back of the car in clear view, so you have to cut a hole somewhere. I cut a hole where my license plate goes, but others have drilled the hole in the rear panel or brake light. Then the alternator wire needs to be routed all the way back to the battery side of the switch. Also, the battery box needs to be sealed and properly vented, or you have to install a firewall (.032" thick steel I think) at rear seat.
Question: why are you guys moving the battery to the rear of the car when there's a wonderful invention known as: DyanBatt http://www.performancedistributors.com/batteries.htm 13 lbs. and no goofy wiring problems or cutoff switches in what are primarily street-driven cars.
Shadow, I like to have as much free space under the hood as possible, so if it doesn't need to be there, it goes. Trunk was next best place. (If only I could move those damned shock towers back there ) Original question, which wire from alternator goes to the switch?
I know it's counter intuitive, but it will work to put the switch on the cold side. 1) If the hot wire grounds out (shorts) during a wreck with the switch on the hot side, it's still going to make a big fire until someone hits the switch. It's a switch not a fuse. Hopefully there are some fusible links and fuses else where in the car. 2) Electricity and plumbling, while similar in principle, don't work the same in your analogy. Your analogy of plugging up the drain only works if the water coming out of the faucet is being fed by the drain basin. Electricity circulates. It doesn't come from some external source. In which case, yes once you plug the drain, the water will stop coming out of the faucet. Placing a switch, in series, anywhere in the loop is going to cause a complete loss of power when the switch is in the open position. It doesn't matter if it's in on the positive or negative pole of the battery. What happens when you disconnect the negative terminal on your car battery? Nothing works right? You can even lay a wrench from the hot side of the battery to the frame and no sparks or fire or anything, because there is no voltage potential to force a current flow. You can test this out with a volt meter if you want. With the negative side disconnected, go from the hot pole to any ground point on the car and see what the voltage says. The only way this doesn't work is if the switch grounds out. Then it's useless. However if that happens wired through the hot side, then you're going to melt down the switch. The safety concern comes more from fuel fires and run away vehicles than it does from electrical fires. Anyone who's actually caught wires on fire (first hand here) knows that's it's generally pretty quick and the wires break after a couple of seconds. There's really no time to run to the back of the car and throw a switch. Then you just need to be quick getting the insualtion and capet that's on fire put out.
If you're dead set on doing it this way, which is fine, then the wire that runs from the alt to the battery + terminal (or the starter) is the one that goes on the switch. So, you'll have your battery hot wire and alternator wire going to one side of the switch, then one big cable going from the other side of the switch to the starter and at the starter post is where you should have your fusible links and other acc power wires. If you still want to have the radio work with the main switch open you'll have to run an additional wire from the radio fuse point to the side of the switch with the battery and alt wire. That will defeat the purpose of the safety switch and still allow a hot wire to ground out though. If you just run from the battery side of the switch to the radio, you also run the risk of burning up your radio.
