Battery kill switch

Dmarstroker · May 13, 2007

Well, I took my car to the track a few weeks ago with the battery relocated and they tested the kill switch with my car running. Problem is that my car stayed on after they flipped the switch. After I turned the car off, then the car would not start. They told me to run it through my ignition system so my car would just shut off completely. Im a newbie when it comes to wiring so any and every help would be appreciated. I know I would need to splice it from the battery cable, but how would I run it through my ignition system? Sorry if this sounds like a stupid question

sweet88gt · May 13, 2007

Do a search on battery kill switch in this forum and you will find a couple of threads with the correct answer. You need to kill the 12v for the altenator. The correct way to do it is in those threads. It helped me with my battery relocate. One question do you have the 2 pole battery cut off switch?? If not you will need to get the correct switch.

Fett · May 13, 2007

Yea, if you have the alternator still connected the car will continue to run....just as if you disconnected a battery in any other car, the alternator continues to provide power for the car.

Most of the guys I know simply unplug their alternator prior to going through tech, so the battery kill switch will shut the car off. Then after they pass tech, they reconnect the alternator. HOWEVER!!! This completly bypasses the whole purpose for the kill switch in the first place, and is not the "safe" or "correct" way to do it. Just pointing it out.

Dmarstroker · May 13, 2007

Fett said:
Yea, if you have the alternator still connected the car will continue to run....just as if you disconnected a battery in any other car, the alternator continues to provide power for the car.

Most of the guys I know simply unplug their alternator prior to going through tech, so the battery kill switch will shut the car off. Then after they pass tech, they reconnect the alternator. HOWEVER!!! This completly bypasses the whole purpose for the kill switch in the first place, and is not the "safe" or "correct" way to do it. Just pointing it out.

I'll try this one time to see if I can slip through the tech. Thanks

jrichker · May 13, 2007

For a battery cut off switch, see http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
is the switch http://www.moroso.com/catalog/images/74102_inst.pdf is the installation instructions.
Use the super duty switch and the following tech note to wire it and you will
be good to go.

Use the Moroso plan for the alternator wiring and you risk a fire. The 10
gauge wire they recommend is even less adequate that the stock Mustang
wiring.

There is a solution, but it will require about 40' of 18 gauge green wire.

Wire the battery to the two 1/2" posts as shown in the diagram.

The alternator requires a different approach. On the small alternator plug
there is a green wire. It is the sense lead that turns the regulator on when
the ignition switch is in the run position. Cut the green wire and solder the
40' of green wire between the two pieces. Use some heat shrink to cover the
splices. See http://fordfuelinjection.com/?p=7 for some excellent
help on soldering & using heat shrink tubing.

Run the green wire back to the Moroso switch and cut off the excess wire.
Try to run the green wire inside the car and protect it from getting cut or
chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp
on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs.
Do not add the jumper between the 1/2" stud and the 3/16" stud as shown it the
Moroso diagram.

How it works:
The green wire is the ignition on sense feed to the regulator. It supplies power
to the regulator when the ignition switch is in the run position. Turn the
Moroso switch to off, and the sense voltage goes away, the voltage
regulator shuts off and the alternator quits making power.

The fuse & wiring in the following diagram are for a 3G alternator. The stock alternator uses a dark green fuse link wire that connects to 2 black/orange wires. Always leave them connected to the starter solenoid even if you have a 3G alternator.

See the following website for some help from Tmoss (diagram designer)
& Stang&2Birds (website host) for help on 88-95 wiring
http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

Dmarstroker · May 13, 2007

jrichker said:
For a battery cut off switch, see http://www.moroso.com/catalog/categorydisplay.asp?catcode=42225
is the switch http://www.moroso.com/catalog/images/74102_inst.pdf is the installation instructions.
Use the super duty switch and the following tech note to wire it and you will
be good to go.

Use the Moroso plan for the alternator wiring and you risk a fire. The 10
gauge wire they recommend is even less adequate that the stock Mustang
wiring.

There is a solution, but it will require about 40' of 18 gauge green wire.

Wire the battery to the two 1/4" posts as shown in the diagram.

The alternator requires a different approach. On the small alternator plug
there is a green wire. It is the sense lead that turns the regulator on when
the ignition switch is in the run position. Cut the green wire and solder the
40' of green wire between the two pieces. Use some heat shrink to cover the
splices. See http://fordfuelinjection.com/?p=7 for some excellent
help on soldering & using heat shrink tubing.

Run the green wire back to the Moroso switch and cut off the excess wire.
Try to run the green wire inside the car and protect it from getting cut or
chaffed. Crimp a 18 gauge ring terminal (red is 18 gauge color code for the crimp
on terminals) on each wire. Bolt one ring terminal to each of the 3/16" studs.
Do not add the jumper between the 1/4" stud and the 3/16" stud as shown it the
Moroso diagram.

How it works:
The green wire is the ignition on sense feed to the regulator. It supplies power
to the regulator when the ignition switch is in the run position. Turn the
Moroso switch to off, and the sense voltage goes away, the voltage
regulator shuts off and the alternator quits making power.

The fuse & wiring in the following diagram are for a 3G alternator. The stock alternator uses a dark green fuse link wire that connects to 2 black/orange wires. Always leave them connected to the starter solenoid even if you have a 3G alternator.

See the following website for some help from Tmoss (diagram designer)
& Stang&2Birds (website host) for help on 88-95 wiring
http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

Thank you...I appreciate it

SMOKEDYA · May 13, 2007

I have the bigger alt. (3G) off a 95. I ran mine like this: Hot off the alt to one side of switch, on that same side of switch run your hot or + off the battery. On the other side of the switch run your hot to the solinoid. Done! I wouldnt bypass it cause if you break or something they will most likly hit your switch and if it dosent kill the car you might get banned from the track?! My buddy just broke an axle this weekend and the first thing they (track offical) went for was his KILL SWITCH! Do it right or not at all. peace

john

GearHd6 · May 18, 2007

I did what JRichker posted above last year to wire my switch and it works like a champ. Follow that exactly and you'll be all set.

onefstsnake · May 26, 2007

why not just wire it to the Neg side of the ign coil?

But I guess that would only cut the motor off and not the rest of the electronics...
gotta love answering your own questions lol...

795.0pacecar · May 27, 2007

I think it should be noted that the studs on the super duty moroso switch are 1/2" not 3/16. So you will have to buy 1/2" ring terminals in order to use this switch. I am in the middle of relocating my battery and I found this out the hard way.

smr · May 29, 2007

not on the 74102 it has two 1/2" studs and two 3/16" studs. I have the 74102 switch in my car. I was just in the middle of running 4 gauge wire back from alternator location to kill switch. I am now switching the wiring to JRichker way. Thanks for great info...

jrichker · May 29, 2007

795.0pacecar said:
I think it should be noted that the studs on the super duty moroso switch are 1/2" not 3/16. So you will have to buy 1/2" ring terminals in order to use this switch. I am in the middle of relocating my battery and I found this out the hard way.

Thank you for the change information. I will update my write up to reflect the changes.

Battery kill switch

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