Wiring diagram showing cutoff switch

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kgwmu

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Does anyone know of a good wiring diagram that includes accessories and a cutoff switch? I need to clean up my wiring because I found that when I turn off the cutoff switch with the car running, it doesn't kill the car.

Some basic info on my car.
  • Keyed power and start
  • I have radio/intercom that is connected to the positive side of the battery
  • Cutoff switch is in line with the ground from my battery
  • A couple accessories are grounded to the chassis (I'm thinking that is part of the problem)

I did save the attached diagram, but it doesn't really show accessories like the radio/intercom that Rugged says to connect direct to the battery. I believe John from Outfront shared this diagram it before the site crash.
 

Attachments

Your battery in and alternator in should be on the same pole on the "off" side of the switch. Everything to be powered should be on the other side.
 
like it said above, the alternator puts out power, peeps are lazy and run that to the starter post, and the starter post on most wiring is a post that they hook up ever possible positive wire to, so anything on the post touching the alternator will have power as long as the alternator is spinning
 
You can also terminate the alternator on the battery, but the positive cable should go to the disconnect switch only, and the starter on the battery post to save amperage from passing through the switch. Nothing else on the battery post or in between (or it won't shut off with the switch).
 
kgwmu said:
Does anyone know of a good wiring diagram that includes accessories and a cutoff switch? I need to clean up my wiring because I found that when I turn off the cutoff switch with the car running, it doesn't kill the car.

Some basic info on my car.
  • Keyed power and start
  • I have radio/intercom that is connected to the positive side of the battery
  • Cutoff switch is in line with the ground from my battery
  • A couple accessories are grounded to the chassis (I'm thinking that is part of the problem)

I did save the attached diagram, but it doesn't really show accessories like the radio/intercom that Rugged says to connect direct to the battery. I believe John from Outfront shared this diagram it before the site crash.
Click to expand...

I don't think I've ever seen a Perko Switch on the ground side of a battery?

Every car is different.

I make my own wiring diagrams from from scratch when wiring a car.

Are you running a one wire alternator? Or?

🤔

P.S. that wiring diagram must be older than dirt. I'd much rather utilize a volt meter, than an idiot light to verify charging.
 
rivermobster said:
I don't think I've ever seen a Perko Switch on the ground side of a battery?

Every car is different.

I make my own wiring diagrams from from scratch when wiring a car.

Are you running a one wire alternator? Or?

🤔

P.S. that wiring diagram must be older than dirt. I'd much rather utilize a volt meter, than an idiot light to verify charging.
Click to expand...
I agree, it does seam like an older diagram, I was just using it as a reference.

Yes, I have a 1 wire alternator.

When I added a cutoff switch to my last car it was on the positive side. To me that made the most sense, so when I seen our new car setup this way it through me off a little. Looks like I have some updating to do in our offseason here.
 
kgwmu said:
I agree, it does seam like an older diagram, I was just using it as a reference.

Yes, I have a 1 wire alternator.

When I added a cutoff switch to my last car it was on the positive side. To me that made the most sense, so when I seen our new car setup this way it through me off a little. Looks like I have some updating to do in our offseason here.
Click to expand...

Start on a big blank piece of paper and a bunch of colored pencils.

Draw the battery on the top left corner, and draw all your consumers at bottom.

(Current show flow down, yes?)

Then start connecting things together, adding fuses,relays and switches as necessary.

Make sure you have a good eraser too! Lol

Eventually,it will all start to make sense, and you'll eliminate any wiring you don't Absolutely need!

It's a LOT easier to do it on paper, than it is on an actual car. 😜
 
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I wired my cut off switch in Baja to the ground, I turn it off, and pull the key, and there is literally zero ground to the car.
I did it this way because I thought it might confuse the average thief.
 
@kgwmu

Start small. Even the toughest things become simple when you break em down to the basics.

I had a customer that wanted power windows, auto closers and power locks, added to his Early Bronco! I had to build all of that stuff from scratch!!!

A few hours scratching my head with my paper and colored pencils, and eventually, I had a map to build from. My kids would make fun of me: check out dad playing with is colored pencils! :ROFLMAO:

But slowly but surely, it became reality...

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Fun, right? lol

20180913_131551.jpg
 
WheresHotBoat said:
I wired my cut off switch in Baja to the ground, I turn it off, and pull the key, and there is literally zero ground to the car.
I did it this way because I thought it might confuse the average thief.
Click to expand...
Only bummer this way is it doesn't work as an emergency shutoff as only the battery is isolated.

Being able to turn off the ENTIRE electrical system (especially fuel pump) in an emergency is a good feature to have.
 
Rockwood said:
Only bummer this way is it doesn't work as an emergency shutoff as only the battery is isolated.

Being able to turn off the ENTIRE electrical system (especially fuel pump) in an emergency is a good feature to have.
Click to expand...
It 100% shuts off 100% of the entire electrical system, there is Zero ground to the car, or any electrical when my key is turned.
 
WheresHotBoat said:
It 100% shuts off 100% of the entire electrical system, there is Zero ground to the car, or any electrical when my key is turned.
Click to expand...
Word. Hard to do on something made of metal with solid engine mounts, shift cables, throttle cables, etc. Lots of things that can carry ground, especially if the battery moves in a bad wreck.

Easier to just land 2 wires to me, but more than 1 way to skin a cat
 
Last edited:
Rockwood said:
Word. Hard to do on something made of metal with solid engine mounts, shift cables, throttle cables, etc. Lots of things that can carry ground, especially if the battery moves in a bad wreck.

Easier to just land 2 wires to me, but more than 1 way to skin a cat
Click to expand...
The car doesn't ground itself, it needs the ground from the battery to the Chassis to get things started. My main ground, goes from the battery, to my switch, then to the Chassis. Kill the switch, and there is zero ground to the entire car.

Battery box and hold down have been thoroughly tested, thanks to the wife. FWIW, this car is almost 30 years old. Been through the ringer and a few variations.
IMG956805.jpgResized_2012-10-06_10-19-45_456_1726920369664.jpegResized_2012-10-06_17-46-28_774_1726920370241.jpegResized_Screenshot_20240921_051312_Facebook_1726920872402.jpeg
 
WheresHotBoat said:
The car doesn't ground itself, it needs the ground from the battery to the Chassis to get things started. My main ground, goes from the battery, to my switch, then to the Chassis. Kill the switch, and there is zero ground to the entire car.

Battery box and hold down have been thoroughly tested, thanks to the wife. FWIW, this car is almost 30 years old. Been through the ringer and a few variations.
View attachment 122421View attachment 122422View attachment 122423View attachment 122424
Click to expand...
In order for your switch to successfully shut everything down with the engine running you would have to land every component’s ground on the switch. ECM ground, fuel pump, relays, all of it. If they’re not on that switch, they’re all grounds to complete whatever circuit they’re on.

If it’s just between battery and the chassis, you have a battery isolator, not an emergency cutoff switch.

I’ve seen crashes where the battery box let go and the battery bounced around the trunk like a wrecking ball. Not much left of the car, the battery is destroyed, but the engine is still running because the alternator is spinning. A quick and brainless way to shut down all electricity in the car is required by every sanctioning body I’ve raced in for a reason.
 
Rockwood said:
In order for your switch to successfully shut everything down with the engine running you would have to land every component’s ground on the switch. ECM ground, fuel pump, relays, all of it. If they’re not on that switch, they’re all grounds to complete whatever circuit they’re on.

If it’s just between battery and the chassis, you have a battery isolator, not an emergency cutoff switch.

I’ve seen crashes where the battery box let go and the battery bounced around the trunk like a wrecking ball. Not much left of the car, the battery is destroyed, but the engine is still running because the alternator is spinning. A quick and brainless way to shut down all electricity in the car is required by every sanctioning body I’ve raced in for a reason.
Click to expand...

This is kinda what I was alluding to, cause that's how boats are wired (no chassis to ground to).

But I've never actually tried it, or seen it done? 🤷‍♂️

Too much work to find out. 😜
 
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