I am wiring my kill switch. I have a 4 gauge cable from the battery to the switch. From there, it needs to go to both the starter and the main fuse box under the hood. I am going to run 4 gauge to the starter and from there build a cable to go from the starter to the fuse box. Seems like that line is fused at 50 amps. That would mean using a 10 gauge cable.

Here are the questions:
- should I overbuild with an 8 gauge cable?
- where to (locally, brick and mortar) buy 8 or 10 gauge cable and connectors?
- which connector have you found to actually fit in the rather small opening of the fuse box?

After that I will cut into the 12 gauge ignition wire at the distributor, wire in the ground with resistor and call it a day. And off to mount the damn thing somehow.

thanks for the help.
S.

 

Although I have wired a few many years ago, my prowess and confidence with electrics is low so I'll let the others respond to the specifics. I would think some of those wire sizes to be bigger than needed but I bow to others more knowledgable on this.

The key is that the running car turns off when you throw the master switch off so the charged power from the alternator must go to the battery side of the switch and not the car side like many do. Fully expect this to be tested when the car firs gets logbooked, you'd be surprised how many people get it wrong. If wrong, the switch can take the battery out of the loop but the car still runs on alternator made power.

I prefer to mount the master switch to the roll cage within easy reach of the driver and of corner workers reaching into the car. Mine is on a welded platform on the mid-level horizontal bar in the main hoop about there a passenger's shoulder blades would fall if the seat was still there.

I sit here in Hilton Head, SC at my in-laws for the holidays and my main goal while here is to draw up a full wiring schematic for the Prod car so I can get started when I get home the first week.

 

are you saying that there will be WORK done on your race car? Say it isn't so!

What I am doing is leaving the alternator alone, but I am cutting off the ignition at the distributor. So the car WILL shut down when the switch gets thrown. Once the engine stops (and the alternator is not generating anymore) there won't be any power anywhere. I believe this to be the best option - and it coincidentally matches the instructions that came with the switch.

thanks for the input and good luck with the diagrams. Let me know if I can help in any way.

 

Home Depot welding cable is ideal! I bought 8 ga from Napa though.. compare prices.

As far as 8 ga being overkill/under. Its not. Its well sized! 10Ga would work very well as well!

napa sells ring terminal connectors. I just crunched them in my bench vise.. No problems at all!

I also got some of those big yellow crimp connectors and some 12ga wire for things like the fuse box etc..

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SJR &raquo;</TD></TR><TR><TD CLASS="quote">
- where to (locally, brick and mortar) buy 8 or 10 gauge cable and connectors?
</TD></TR></TABLE>

Probably the most cost effective option for the wire would be Home Depot / Lowes. For the connectors, head to a stereo shop or Radio Shack. The connectors may be too large to connect to the main box, but usually the 8/10ga are beefy enough that you can cut them to fit, and still maintain a good connection. Any stereo shop will have wire as well, but it'll be about twice the price as HD would be.

 

I think I ran my four post switch that way originally. It didn't work.

I have the longacre kill switch. I interupted battery positive with the switch wiring it into the larger post. I interupted the distributor cable (distr. to under hood box) by wiring it into the smaller post. That worked.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRX Lee &raquo;</TD></TR><TR><TD CLASS="quote"> If wrong, the switch can take the battery out of the loop but the car still runs on alternator made power.

</TD></TR></TABLE>

How's that? If the power gets shut off, the computer isn't going to have power so the engine won't run.

 

That's the point. The power still comes from the alternator.

Some points. SCCA REQUIRES that all circuits be cut off, except electricaslly operated fire supression systems. (Still waiting to see one of these.) The test that needs to be done are these. Start car. Kill car with kill switch. Take test light and probe everywhere looking for voltage. This includes ALL terminals on the alternator. Not that many tech inspectors will do this.

My next issue is this. This rules were written before on-board computers. If you take away the power form the computer, doesn't the system have to relearn itself?? Doesn't that take more time than you have before the next session, assuming you have the space to drive it thru all of its routines??

If so, I would figure a way to not loose the computer memory if it were my car.

Inquiring minds want to know.

 

For cables, I used a set of jumper cables and cut the ends off.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civicrr &raquo;</TD></TR><TR><TD CLASS="quote">I think I ran my four post switch that way originally. It didn't work.

I have the longacre kill switch. I interupted battery positive with the switch wiring it into the larger post. I interupted the distributor cable (distr. to under hood box) by wiring it into the smaller post. That worked.</TD></TR></TABLE>

that's what I am doing, interrupting the distributor power. Unless you meant alternator.

Grumpy:
Given the tests you propose, my way should work. you hit the kill switch, the engine dies. When the motor is stopped, there is no battery connection to anywhere, hence no power on any circuit - unless there is a rather large capacitor somewhere that has enough stored energy to light up the test light momentarily...
As far as the computer learning, I would be worried on a newer model, but I don't think it will affect my little old OBD0 computer that doesn't even have an O2 sensor plugged in.

I finished wiring it last night. It is not mounted yet, and I am a little worried about one thing:
those two big-*** posts connected to battery positive are rather bare, and rather too close to other metallic objects for comfort. I temporarily insulated them with some electrical tape, but I am not satisfied with this. Any suggestions appreciated. BTW, it will be mounted to the A-pillar tube of the roll cage, on a welded tab (typical location).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SJR &raquo;</TD></TR><TR><TD CLASS="quote">
those two big-*** posts connected to battery positive are rather bare, and rather too close to other metallic objects for comfort. I temporarily insulated them with some electrical tape, but I am not satisfied with this. Any suggestions appreciated. </TD></TR></TABLE>

In the electrical shop here, we have all types of shrink wrap with varying shrink ratios. There is some that starts off pretty large to slip over large battery terminals, and can shrink down to 16ga. I would think that you could find some retail somewhere.

 

To answer you baseed on our build-make the cable to the fuse box the same guage as the stock one. I am assuming that you will also be breaking the connection out of the fuse box for the Ignition switch and underdash wiring so that you are positive that no power can go to the ECU, etc. Otherwise you can run the risk of the engine not shutting off.

What I did was to use the Krause & England arrangement for the switch under the hood-thereby not needing bulkhead connectors (personal choice). They use a pull cable that can be located either on the outside of the car or on the dash. Moving along-the wiring from the battery uses a standard cable to a Longacre 2-pole single throw switch. The 2 large terminals are the battery on one side and the starter and fuse panel on the other large lug. The second pole (small lugs) breaks the cable that is indeed a 50 amp line (white/black stripe (If memory serves me)) going from the panel to the Ignition circuits. By using this arrangement-ALL power is removed from the ECU, pumps, etc. Not only that-the Field of the Alternator no longer has a path and that is critical to insuring that the engine shuts down. I do not use a resistor or anything else in my cars and this arrangement does not require it. What one must remember is that this is a shutdown for cause device. We use it to insure that there is no power even while the car is on the trailer.
Many people have different ways to wire and they work. I put the switch where it is because I did not want heavy wiring in the cockpit. I also did a remote cable as it is a another way to insure that the switch will be turned off.

 

I also used jc836 method to wire mine it. It was the simplest way to wire it in by far~! I made up a crude diagram to show the path...


Here it is.





The wht/blk wire should come from the ignition switch and go to the fuse box under the hood. You can catch that wire running in the loom that goes to the fuse box, cut it in 2, and run each side to the secondary switch on the cut off.

Hope this makes sense!
The diagram kinda helps me because it's easier to see than try to explain!

 

I think a bunch of us are saying the same thing in different ways so that we can understand it ourselves.

Using the diagram above, for me, the white/black would be the alternator output that connects to the underhood fuse box.

 

right, and in my case, it is the black/yellow wire that supplies juice to the ignition coil.

I am pretty sure that all three methods work. Is one better than the other? I dunno. As long as they all end up stopping the car...

 

In the diagram below, there is a wire on the right spliced into the alternator cable running to one of the smaller posts. My question is can I just run a wire from the alternator side large post to the smaller post? Or do I have to splice into the alternator cable up stream like in the picture?

 

couple of things:

1- electrically, it makes no difference whether you connected the two terminals at the switch or if you ran a wire all the way from the other end of the circuit. Which brings up the second point

2- on the right side of the diagram, the cable hooked up to the large post is not connected to the alternator, it is connected to the underhood fuse box ( = main power input for the whole car). The alternator also feeds into the underhood fuse box, albeit on a different terminal. Having the circuit diagrams for your particular car would be helpful here to avoid confusing yourself.

3- EDIT: make sure to hook up the drain wire (with the resistor) to the set of poles marked "1". These poles work opposite from the other ones. When the "large" circuit and the "2" circuits are closed, the "1" circuit is open, and vice-versa.
HTH.

Sebastien, electrical engineer turned to the dark side (software engineering)

 

Thanks for clearing that up. I guess if I had spent a little more time searching I would have noticed this:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">How to wire:
Killing battery output: "Big wires"
--------------------------------------
1) Remove wire from battery to starter & discard.
2) Remove wire from battery to main fuse box & discard
3) Run wire from battery to kill switch
4) Run wire from "Output" of kill switch to starter and to main fuse box
Killing Ignition "Little wires"
-------------------------------
1) Find power to coil (On EG it is black/yellow wire coming from ignition)
2) Cut wire and connect one end to one "2" terminal and the other to the other "2" terminal

Grounding alternator / fuse box "little wires"
1) Connect output side of "big terminals" (going to starter) to one terminal marked "1"
2) On other "1" terminal connect piece of wire to supplied resistor.
3) Connect other side of resistor to ground.

What happens: Stated simply as I can:
When the switch is "on"
----------------------------
- The battery is connected to the main fuse box through the switch.
- The power to the coil is connected to the distributor through the switch
- The resistor does nothing - it's not connected to either big terminal

When the switch is "off"
----------------------------
- The battery is no longer connected to the main fuse box
- The power is cut to the coil so the car stops running
- The main fuse box (and the alternator) are grounded through the resistor -preventing any voltage spikes from occuring.

The key thing is to make sure you connect the resistor / ground to the right side of the big terminals - you don't want to ground the battery by mistake.

Note that you never touch any of the alternator wires.

- Phillip
</TD></TR></TABLE>

 

a kill switch that simply disconnects the main relay wouldn't fit the rules, would it?

 

"supplied resistor"

do they typically come with the kill switch?

 

Thanks to prkiller for the diagram. This does work and complies with both SCCA and NASA rules for shutdown of the car. The resistor idea is not bad-just not needed. The wire we are referring to supplies power to the Ign switch and other things under the dash.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mstewar &raquo;</TD></TR><TR><TD CLASS="quote">"supplied resistor"

do they typically come with the kill switch?</TD></TR></TABLE>

yes

 

Thanks for all this info guys, I'll hopefully be needing it in a few weeks and have it here as a reference. I bought my kill switch in 1998 (yikes!) and couldn't find the wiring instructions.

My set-up for the F Prod car is going to be a bit different from most guys here as my car has had all of the factory wiring removed and discarded except for the basic FI control and the brake light wiring downstream of the pedal switch. I have a simple racing panel (Quikcar?) with 6 individually fused toggle switches and a starter button (Ign., Fan, Fuel Pump, Wipers, and spares) then a seperate non-switched fuse block for circuits that will always be hot when the kill switch is on (brake lights, ECU, dash guages, heated 02 sensor, field power for the alternator (?), etc.).

I am still a bit corn-fused about needing to put relays in the fan (supplied), wiper (reusing the stock motor), and fuel pump. Since each of those seperate circuits will be run through their own toggle switches and fuses and can have any wire sizes needed to run to them, I would think that I can skip the relays and keep the curcuits simpler. Any thoughts? I do plan to get an inertia interupting switch to put into the fuel pump power line so power is cut in case of a shunt. I hear the Trans Am sereis uses a common, stock Ford switch so I will get one.

I have chicken scratched out a basic wiring diagram but have no scanner available to be able to post it for you guys to see and show me what needs to be altered. Knowledgable input in layman's terms is appreciated.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CRX Lee &raquo;</TD></TR><TR><TD CLASS="quote">I am still a bit corn-fused about needing to put relays in the fan (supplied), wiper (reusing the stock motor), and fuel pump. Since each of those seperate circuits will be run through their own toggle switches and fuses and can have any wire sizes needed to run to them, I would think that I can skip the relays and keep the curcuits simpler. Any thoughts? </TD></TR></TABLE>

Here's my thinking:
1- you use direct circuits, using the appropriate size wire for each item, from the power source to the switch to the item to ground (or put the switch in the ground circuit, whatever)

2- you use one common large "power rail" that goes to all the items (you'd have to add all the max draws for each item and see what that comes up to) and then use small wires to relays for each item.

Option 2 is only marginally more complex (one more power circuit than option 1) and may end up being lighter, depending on your total amperage. You can also keep all the (relatively) high current circuits out of harm's (and cockpit's) way. On the other hand, if the power circuit fails, you lose power to everything.

Option 1 provides more redundancy for each item, but puts more current in the cockpit, close to the driver = potentially close to oil/fuel lines? Then again, this is coming from the guy who just wired two 4ga cables carrying around 60amp right by his left hand and face, on the A-pillar tube... That's actually on toonight's agenda: clean up some of the wiring routing and try to see if there's any risk of shorting the battery to ground. I wonder if anyone make an inline fuse for 4ga cable?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SJR &raquo;</TD></TR><TR><TD CLASS="quote">1- you use direct circuits, using the appropriate size wire for each item, from the power source to the switch to the item to ground (or put the switch in the ground circuit, whatever)

2- you use one common large "power rail" that goes to all the items (you'd have to add all the max draws for each item and see what that comes up to) and then use small wires to relays for each item.

Option 2 is only marginally more complex (one more power circuit than option 1) and may end up being lighter, depending on your total amperage. You can also keep all the (relatively) high current circuits out of harm's (and cockpit's) way. On the other hand, if the power circuit fails, you lose power to everything.

Option 1 provides more redundancy for each item, but puts more current in the cockpit, close to the driver = potentially close to oil/fuel lines? </TD></TR></TABLE>
I think I will go with Option 1 as each circuit is seperate and isolated so I think future problems would be easier for me to troubleshoot. The Quickcar panel has a main hot wire line that breaks into seperate switched and toggled circuits so all I have to do is run it to my kill switch then run one hot to each target (fan, pump, etc.) then ground them solidly. If this gets me out of the need to have relays then I am happier as it cuts down the need for extra little switch circuits, several relays and brackets that risk vibration failures, etc. The targets are spread around the car enough that running a single power circuit to everything will end up with quite a bit of wire and I think might complicate troubleshooting downstream that dedicated circuits and fuses will eliminate.

Since the starter hot wire will have it's own big power cable going straight there, I can't imagine that the other items will need a huge cable to feed them juice from the switch/fuse panel. Does the starter button circuit get a seperate relay or does the power up and kick-in of the starter bendix take care of that?