Battery Cut-Off Switch

DocG · Feb 20, 2009

Hey all. Well I realize that since my car has a battery relocated to the trunk, in order to run the track I need a cut-off switch.

Does anyone have one? Any suggestions on a good one and the best place to mount it? I really hate to tear up my car more than necessary. I'm assuming installation is just putting it inline with the cable from the battery to the alternator right?

I'm currently running the stock alternator but looking to upgrade to a 3G soon, so I want to make sure my switch will handle that.

Any pics, links, tips would be great! Thanks!

jrichker · Feb 20, 2009

For a battery cut off switch, see Moroso : Category Display
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 Ford Fuel Injection How To Solder Like a Pro 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 a turn
on signal 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
Mustang FAQ - Engine Information 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

Rear mounted battery ground wiring. Follow this plan and you will have zero
ground problems.

One 1 gauge or 1/0 gauge wire from battery negative post to a clean shiny spot
on the chassis near the battery. Use a 5/16” bolt and bolt it down to make the
rear ground. Use a 1 gauge or 1/0 gauge wire from the rear ground bolt to a clean
shiny spot on the block.

One 4 gauge wire from the block where you connected the battery ground wire to
the chassis ground where the battery was mounted up front. Use a 5/16” bolt
and bolt down the 4 gauge engine to chassis ground, make sure that it the metal
around the bolt is clean & shiny. This is the alternator power ground.

The computer has a dedicated power ground wire with a cylindrical quick connect
(about 2 ½”long by 1” diameter. It comes out of the wiring harness near the
ignition coil & starter solenoid (or relay). Be sure to bolt it to the chassis ground
in the same place as you bolted the alternator power ground. This is an
absolute don’t overlook it item for EFI cars
Note: The quick disconnect may have fallen victim to damage or removal by
a previous owner. However, it is still of utmost importance that the black/green
wires have a high quality ground..

The screwdriver points to the common body ground for the alternator, battery and computer.
Picture courtesy timewarped1972

Crimp or even better, solder the lugs on the all the wire. The local auto stereo
shop will have them if the auto parts store doesn't. Use some heat shrink tubing
to cover the lugs and make things look nice.

DocG · Feb 20, 2009

Woah! More complicated than I thought it might be.

Thanks though! That should get me through it. I'll save this and hopefully get the switch soon!

anotherstangfan · Feb 20, 2009

i had the cut off switch under my license plate in the back, it was already there when i bought the car.

DocG · Feb 21, 2009

anotherstangfan said:
i had the cut off switch under my license plate in the back, it was already there when i bought the car.

Pics?

When you say under.....do you mean vertically, or hidden behind it?

faststang90 · Feb 21, 2009

my kit

i use the rod kit and had to put the rod out the back but its a full race car

View attachment 269799

View attachment 269800

View attachment 269801

DocG · Feb 21, 2009

faststang90 said:
i use the rod kit and had to put the rod out the back but its a full race car

Thanks!

I thought about doing the rod kit like that, and putting the hole directly behind the license plate.....thus when I'm at the strip take off the plate and attach the pole if I can somehow hide the switch inside the hatch. Other times the plate would hide the hole.

faststang90 · Feb 21, 2009

i put it like that

i put it like that because my car has a rear wing on it and i did not want people to miss up the wing if they ever have to use it.

anotherstangfan · Feb 23, 2009

i only have one picture but you can kind of see it on the right, it was a red knob, it is behind the plate so the plate was bent out a little.

DocG · Feb 28, 2009

anotherstangfan said:
i only have one picture but you can kind of see it on the right, it was a red knob, it is behind the plate so the plate was bent out a little.

Do you just take off the plate at the track?

I'm looking at ordering the Moroso switch today. I might go ahead and order the push/pull kit too and try to mount the switch remotely. I want it to be as invisible as possible.

Bullitt347 · Feb 28, 2009

Mine is also behind the rear license plate, but I have the plate spaced out away from the switch so the plate is flush with the taillights. At the track I just remove the rear plate. Also mine is more centered to the plate so you cannot tell it is there when the plate is on.

rednotch88 · Feb 28, 2009

I cut a hole through my plate and have the switch covering the last letter when off,and when its on it don't cover any numbers.Look pretty slick probably illegal too,but I'm from Chicago .
Ill get you some pictures when I get car back.You can see a big dimple facing outwards on the bottom right hand side if you take plate off I just used that as a template.Good Luck
I hate that bar type cut off to messy for me.

KJ

DocG · Mar 1, 2009

rednotch88 said:
I cut a hole through my plate and have the switch covering the last letter when off,and when its on it don't cover any numbers.Look pretty slick probably illegal too,but I'm from Chicago .
Ill get you some pictures when I get car back.You can see a big dimple facing outwards on the bottom right hand side if you take plate off I just used that as a template.Good Luck
I hate that bar type cut off to messy for me.

KJ

I actually thought about mounting it to the plate. In KY there is a space in the middle, not sure if it would block anything or not.

I've ordered the Moroso superduty switch. Went ahead and ordered the push bar as well. Once I get it all I'll find the best way to mount it I guess. If I don't uset he bar I'll just sell it or return it.

I do like the idea of spacing out the plate though....I'd imagine that's pretty easy to do and seems like a great way to hide the switch.

Thanks for the ideas guys!

DocG · Apr 20, 2009

Ok, finally got a chance to install this thing!

I've got the switch installed and everything is good.

I'm running the alt wire. I'm using 14 gauge wire cuz its what I have.

Can someone help me with the install for the alt wire for a 3g. I have a green with a stripe? Is that the one???

Am I supposed to cut it....wire one end to my switch, and then loop back to the other end???? Or actually connect it all together? From the pic above, I envision one long loop to the switch and back??

Where does this harness goto? If I can find the "other" end of it near the solenoid then that'll save me running extra wire all the way to near the plug.

HALP!

LaserSVT · Apr 20, 2009

You interrupted my conversation with a 19 year old stripper for this?

DocG · Apr 20, 2009

Like he was gonna get anything more than his 20 bux worth.

Next.

DocG · Apr 20, 2009

Come on.....anyone?

A battery cutoff with a rear mounted battery with a 3G alt.?

jrichker · Apr 20, 2009

DocG2828 said:
Ok, finally got a chance to install this thing!

I've got the switch installed and everything is good.

I'm running the alt wire. I'm using 14 gauge wire cuz its what I have.

Can someone help me with the install for the alt wire for a 3g. I have a green with a stripe? Is that the one???

Am I supposed to cut it....wire one end to my switch, and then loop back to the other end???? Or actually connect it all together? From the pic above, I envision one long loop to the switch and back??

Where does this harness goto? If I can find the "other" end of it near the solenoid then that'll save me running extra wire all the way to near the plug.

HALP!

Follow the trail of breadcrumbs in my previous post in this thread...
The wire at the alternator is green with a red stripe.
Cut it into and add the extra wire needed to run it to the battery switch and back.
There will be two wires that run to the battery switch.
Connect the wires you just added to the two small terminals on the Moroso switch.

The green/red wire orginates under the dash were it connects to the Battery light on the instrument cluster.
Unless you are really strangely built, getting to anything under the dash is a pain in the neck...

See the following diagram from TMoss for some further help...

b]Diagram courtesy of Tmoss & Stang&2birds[/b]

DocG · Apr 20, 2009

Yup....I'm a hard head. THat's what I was looking for.

Thanks man!

DocG · Apr 20, 2009

I found that wire near the solenoid.......

Battery Cut-Off Switch

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