• Welcome to ClassicBroncos! - You are currently viewing the forums as a GUEST. To take advantage of all the site features, please take a moment to register. It's fast, simple and absolutely free. So please join our community today!
    If you have problems registering or can't log into your account, please contact Admin.

Electric Shut Off switch, advice needed.

SDlivin

Sr. Member
Joined
Feb 5, 2010
Messages
781
Loc.
San Diego
Going to try to explain this without pictures, and see where that gets me.

Okay, so based on many individuals suggestions (as well as an article in Bronco Driver Mag), I have suggested to install a Master Battery Disconnect Switch.

I'll explain my challenge and then how I have it wired.
With the switch off, no power. Good! When truck is running and then I turn off switch, truck continues to run. Now I know this is because it is running off the Alt Power and the Batt Disco switch is having no affect.

How I have it wired now;

From Batt + to Batt Disco Switch, Other Side of Batt Disco switch to Starter Solenoid, Same Post of Starter Solenoid I have an 175A Mega Fuse attached going to the 3G B+ Terminal.

So in the Bronco Driver Article it says to connect the 'Hot' Wire from your 1 wire alternator (which actually has 3 wires) to the Batt Disco switch and this will kill the truck during running when the switch is tripped.

So I guess my question is what wire from the Alt goes to the Master Batt Disco Switch? 4ga B+ Terminal Wire? Yel/Wht 'A' wire? or Lt Grn/Red 'I' wire?

Thanks!

-Robert
 

G's Baja Bronco

Bronco Guru
Joined
Aug 7, 2010
Messages
1,362
Loc.
Sunny SO CAL
I would imagine that what you want is to stop the power going to the ignition. I would connect the 4 GA alternator wire to the battery side of the cut off switch. this way, when the switch is activated (engine running) it will continue to charge the battery, but engine will turn off, since there is no power going to the ignition.

G
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,980
Loc.
Memphis, TN, USA, Earth, Milky Way
...it is running off the Alt Power...
That's VERY bad for the alternator and every other electronic device on the vehicle. You should never run an alternator without a battery connected to it. Here are 3 safe & effective ways to install a kill switch:

...connect the 'Hot' Wire from your 1 wire alternator (which actually has 3 wires) to the Batt Disco switch and this will kill the truck during running when the switch is tripped.
No, it'll continue to run for a few hours, until the battery gets too weak to power the ignition module & coil (in addition to any other electrical loads you might have turned on), and it'll cause the ALT light to come on, and it could damage the alt, just like the other way you described.

I haven't read that article, but from your description, it doesn't sound right.
 

G's Baja Bronco

Bronco Guru
Joined
Aug 7, 2010
Messages
1,362
Loc.
Sunny SO CAL
?:? wait a minute, why would you activate the main battery power kill switch with the truck running??

I think the answer is, turn the engine off, then apply the battery switch. done, no one can hot wire it now.

I was just pondering out loud;D

Let me know if I am missing something, I am doing this switch install on my brothers 74 tomorrow, he bought his at HF for 5 dollars.

G
 
OP
OP
SDlivin

SDlivin

Sr. Member
Joined
Feb 5, 2010
Messages
781
Loc.
San Diego
Understood about running the car off the alt power alone! I am NOT planning on doing that. I just tested it for 2 seconds to see if I was getting the results I was looking for.

Let me explain a little bit more on the reasoning behind installing this switch.
1. Anti-Theft
2. Removes draw from Batt when sitting.
3. In case of Trouble (tipped over on the trail spilling gas everywhere, or electrical fire under hood), and I or others are stuck in the cab, a simple remote kill switch that others can get to, may come in handy.

Number 3 above is the primary reason behind the Bronco Driver Article.
Issue 25, Jan/Feb 2007, pg 78, 'Kill Your Horse...Without Firing a Shot'. Both examples listed above were expanded on.

True, I may never find myself in either of those situations, but thought if it was a simple way to wire it, since I am already putting in the switch, then why not....?
Also, plan on running the Hot lead wire from my MSD box to the other side of the switch.... This is after reading someone's post a few days ago about their MSD box melting.... With the truck OFF in his gargage.
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,980
Loc.
Memphis, TN, USA, Earth, Milky Way
...a simple remote kill switch that others can get to, may come in handy.
It might, but you'd have to explain to everyone in the vicinity before you go wheeling so they'd all know 1) that your truck HAS such a switch, 2) where it is, and 3) under what conditions you'd like them to kill it.

That's a lot more hassle than (and not nearly as effective/reliable as) just building in an automatic kill switch, like an inertia switch, an oil pressure switch, or a seat occupancy switch, or all of them.
...if it was a simple way to wire it, since I am already putting in the switch, then why not....?
It's not a simple or safe way to wire it since you can't make one switch do all that (as you learned). If you try, you'll create MORE of a fire hazard by running heavy UNfused battery wires all over the vehicle.

Let's start from the beginning: what's the primary goal you're trying to accomplish? Theft prevention, crash safety, or battery storage?
 
OP
OP
SDlivin

SDlivin

Sr. Member
Joined
Feb 5, 2010
Messages
781
Loc.
San Diego
It might, but you'd have to explain to everyone in the vicinity before you go wheeling so they'd all know 1) that your truck HAS such a switch, 2) where it is, and 3) under what conditions you'd like them to kill it.

That's a lot more hassle than (and not nearly as effective/reliable as) just building in an automatic kill switch, like an inertia switch, an oil pressure switch, or a seat occupancy switch, or all of them.It's not a simple or safe way to wire it since you can't make one switch do all that (as you learned). If you try, you'll create MORE of a fire hazard by running heavy UNfused battery wires all over the vehicle.

Let's start from the beginning: what's the primary goal you're trying to accomplish? Theft prevention, crash safety, or battery storage?

Agreed, it looks like I'm fine with theft prevention and battery storage. I wired it like the main kill diagramn you supplied.
Batt + to Switch, Switch to Starter Solenoid. Everything else the same.

I figure I'll run the MSD box and Aux Fuse Box (other thread you helped me out on) off the back side of the Main Kill switch as well, instead of direct to the battery. This way everything will be shut down.

You see any challenges with this?

Thanks for the help.
 

Steve83

Bronco Guru
Joined
Jul 16, 2003
Messages
8,980
Loc.
Memphis, TN, USA, Earth, Milky Way
If that's your goal, then that's the right way to do it safely. Hook up everything as if the battery switch wasn't there. Tie the new fuse block's power feed to the starter relay's hot post.



Then put the kill switch between there & the battery (+) to shut down the whole truck. But even disconnected, the battery will still drain slowly due to internal resistance. So you need to either charge it periodically (easy to forget), or install a battery maintainer charger (either solar or 110VAC). Read this:

 
OP
OP
SDlivin

SDlivin

Sr. Member
Joined
Feb 5, 2010
Messages
781
Loc.
San Diego
Batt Removable Kill Switch Installed....

Thanks for the help.

Basically goes from Batt + to switch, then from Switch to Starter Solenoid.
 

Attachments

  • batt pwr switch.jpg
    batt pwr switch.jpg
    107.2 KB · Views: 14
  • batt pwr switch 1.jpg
    batt pwr switch 1.jpg
    105.1 KB · Views: 11
  • batt pwr switch 2.jpg
    batt pwr switch 2.jpg
    94.6 KB · Views: 13

RRRAAAYYY2

Bronco Guru
Joined
Nov 10, 2004
Messages
1,684
Loc.
Brantford, Ontario
Alternator output should go directly to the battery, not the kill switch. This allows the battery to filter the output of the alternator. Which is the biggest source of noise in your vehicle. If you have dual posts, put the positive on the side post, and everyting else connected to the top post.

If you speak with MSD they have bee nasking racers to put the power supply wires directly to the battery as well. This helps eliminate noise issues with their boxes. A good noise filter on the line will help a lot too. $25 and it offers tons of benefits.

Removing the battery from the alternator while it is charging is dangerous. I have seen the back of alternators blown apart because of this. Even 2 seconds, even any seconds will damage the diodes. Dont ever do it. Never. :)
 

knack

Contributor
Sr. Member
Joined
Feb 2, 2007
Messages
832
When I hooked mine up, I installed it on the (-) side, between the battery and chassis ground, to avoid having more (+) cables and connections to worry about. I shut it off whenever I'm not using the truck, just to make sure nothing drains the battery. It's also there for emergency use, but hopefully I won't need that. I also have my fuel pump wired through an oil pressure switch.
 
Top