13 replies to this topic

[Nathan Pring]

Hey guys, been ready old threads about using the alternator exciter wire to hook up to 4 post cut of switches.  Seems the old photos are missing from the posts and i'm definitely a visual guy.  Can someone confirm on the attached photo that i'm looking at the correct wire?  And is it better to intercept it before or after the plug (towards the battery)?  Cheers from an electrically challenged individual...

Attached Files

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[LarryKing]

I don't know if the "Drago method" is the same as the "Dave Wheeler method" - here's Dave's way in his own words. One caveat, you must leave the switch in the on position at all times otherwise it will drain the battery.

 

"I've let you guys talk about cutting wires, electrical problems and no starts for a while. Here's how I do it and why.

Anytime you break into the factory wiring harness you are looking for problems. Also, in a racecar you never want ANY chance of loose connections or power lose in the fuel or ignition systems. So, why does everybody insist on doing it this way?

I mount my switch on the rollcage about where the passengers right shoulder would be. I use a single pole switch with just 2 connecters.

Start by removing the positive battery cable from the car all the way to the starter. Remove all the tape and clips so it is a free standing cable. Route the cable back through the evaporator hole into the interior. Secure the cable to the trans tunnel with adel clamps. Cut the cable to length and with the proper sized lug attach to the switch. The left over cable is not long enough to reach back to the battery so you will need to purchase a battery cable to go from the battery to the switch.

To get the car to "kill" required some thought and a lot of looking at the wiring diagrams. But it is actually easy.

Remove the battery lead(white larger wire) from the alternator output lug. Cut the connector off and install a larger eyelet. Remove the nut from the starter cable and install the white wire directly to the starter.

Using 10 guage wire about 13 feet long connect the alternator post to BATTERY side of the kill switch. YOU'RE DONE

When you turn the switch off the battery is disconnected AND since the alternator output is hooked to the battery only the car will die. No cutting of wiring harnesses, no blown ECU, no worries mate!!!!"

[LarryKing]

Another classic Dave W post:

 

"Here's how I do it.

I always mount the switch in a location that the driver can reach from the seat WITH belts on. It is really anoying to have to get out of the car when it won't start 'cuz you forgot to turn the master back on. I prefer on the cage near the right rear seat belt tower.

I also always switch the positive cable.

I begin by removing the positive battery cable from the rear to the front. Disconnect from the battery and feed it down under the car. Remove all the tape and plastic loom. Clean it why you are at it. It is not neccesary to remove it from the starter. Leave the starter as is for now.

Feed the entire cable through the ac hole in the firewall, into the interior. Secure with tie wraps or adel clamps. Cut off the battery cable connector and install an eyelet end. Depending on your routing you should have 1-2 feet of extra cable that can also be trimed off. The eyelet end can be crimped on if you have the tools or NAPA sells a nice screw together cable end that requires no special tools.

Connect your original cable with the new end to one side of the switch. Purchase a new battery cable of the correct length to go from the +battery teminal to the other switch terminal. do not connect the battery yet.

This is the part that is hard to describe so follow close. Remove the big white wire from the side of the alternator. The wire loom is usually pretty bad, I clean up the wires why I am here. Cut off the connector from the white wire. Replace it with a larger eyelet. Remove the nut from the battery cable teminal of the starter. Install the white wire with larger eyelet onto the starter and reinstall the nut.

Using 10-12 guage wire, run a new wire from the alternator to the BATTERY side of the master switch. I run it alongside the already relocated batery cable.

Hook up the battery and you are done.

Having spent 25 years fixing cars I have found that anytime you splice into an OEM harness you are looking for trouble. This method requires no modification other than cahnging a connector and rerouting the cables.

One other item that I found the tech guys are looking for is that the cables be insulated at the master switch as well as at the battery. A pice of tape was acceptable at the Sebring race.

Another 2 cents"

Dave

[Jim Drago]

I use Daves method on all the cars now as well since we have moved the kill switch to center the dash. 

[Dave D.]

Yup, Gotta agree, it's simple and works on NA or NB or MX-5 too.

[Ron Alan]

I'm NOT an electrical person...but here is a slight variation to Daves method for NB1 cars that seems to work well! This uses a 4 post kill switch at the passenger side of cage right above seat belt tower. 

 

1.  Disconnect power from battery and re-route to kill switch(load side if it matters?). With the package tray cover removed you can see this wire come into the trunk area...you can choose to cut it shorter or just cut off the factory battery clamp and install an eyelet terminal for the kill switch. Run a new piece of cable from the kill switch to the battery(unfortunately factory wire isn't long enough to interrupt and use both pieces this way).

 

2.  Since you have the passenger tray cover off you will see a piece of harness that comes over from the driver side in front of the fuel tank area. It ends at a connector attached to the side of the seat belt tower. There is a gray/red wire(same wire color you see at alternator)that is exposed. Cut this wire and connect 2 wires to either side and run to the 2 smaller terminals on the kill switch...effectively interrupting this field wire. Done!

 

Basically this method allows you to leave all wires in the engine bay factory...nothing to remove/disconnect/add. Everything is in one spot and very easy access!

 

I'm in the process of a NB2 build and I just checked to see if this 03 car is the same...it doesn't seem to be as the gray/red field wire is not present??

 

Another little trick using Daves method is to use the white wire that comes off the Alternator to power a fuse block(for all your add on goodies you need power for)rather than just connecting back to starter!

[Jim Drago]

 

 

I'm in the process of a NB2 build and I just checked to see if this 03 car is the same...it doesn't seem to be as the gray/red field wire is not present??

 

It's not there

[Nathan Pring]

Thanks all, appreciate the answers!  Id much rather not cut into the harness so Dave's method sounds great.

[ngng]

I know this is an old thread, but all sources seem to point here. Finally am at a point where I need to install a cutoff in the NA8 I'm building to replace my crashed NA6! I have a both a 2 and 4 terminal cutoff. What is the preferred method these days?

[38bfast]

For the last 10 years we have been using a solenoid in the trunk with a fused low amperage push to stop switch on the dash. We have seen too many problems with the mechanical high amp kill switches failing intermittently. By using the solenoid in the trunk when the car is killed only about a foot of hot wire is left in the car and you can have as many kill switches you want in the car. In some cases we have put a push to stop button in both the left and right eyeball vents so the safety crew can easily access killing the power from both sides of the car. Putting the push to kill switch in the LH eyeball vent is about the best place for the driver to kill the car. And because its low amperage wire (18ga) you don't have to deal with running the heavy amp 4ga wire behind the dash. This is a very common system used in pro level cars and general aviation. 

[ngng]

For the last 10 years we have been using a solenoid in the trunk with a fused low amperage push to stop switch on the dash. We have seen too many problems with the mechanical high amp kill switches failing intermittently. By using the solenoid in the trunk when the car is killed only about a foot of hot wire is left in the car and you can have as many kill switches you want in the car. In some cases we have put a push to stop button in both the left and right eyeball vents so the safety crew can easily access killing the power from both sides of the car. Putting the push to kill switch in the LH eyeball vent is about the best place for the driver to kill the car. And because its low amperage wire (18ga) you don't have to deal with running the heavy amp 4ga wire behind the dash. This is a very common system used in pro level cars and general aviation. 

 

Ralph, do you have any more details on this?

[38bfast]

Ralph, do you have any more details on this?

like what? 

[ngng]

like what? 

 

What relay did you end up using? There was another thread where somebody mentioned using the Stancor 586-903 which coincidentally I've used for the glow plugs on another truck. How are you ensuring the alternator is also killed?

[38bfast]

What relay did you end up using? There was another thread where somebody mentioned using the Stancor 586-903 which coincidentally I've used for the glow plugs on another truck. How are you ensuring the alternator is also killed?

Wire the alternator the same as a mechanical 2 post switch. Alternator wire to hot side of the solenoid 100A fused. Any high quality continuous duty relay works. We have used white rogers or Aircraft spruce has some.