How can i wire an alt kill?

[-Matt-]

I need to wire a way to kill my alternator (and rest of car?) when my battery disconnect switch it thrown. Google and other searches come up nil. Please help.

Thanks

Matt

[FordNut]

Just wondering, does the kill switch have to disconnect the alternator? I know it has to disconnect the battery and it has to kill the engine. It should be ok to connect between the fuel pump impact switch and the FPDM (or BAP) for the kill switch part. That will kill the engine by shutting off the fuel pump(s).

[fastblackmerc]

Use a battery disconnect switch.

http://www.tecknowledgey.com/catalog/default.php?cPath=135&osCsid=0ebb02606832bff61b57284 6316bcd70

http://www.nextag.com/battery-disconnect-switch/products-html

http://shop.ebay.com/items/battery%20disconnect?_dmd=1&_sop=12&rvr_id=&keyword=battery+disconnect&crlp=1900873763_1&MT_ID=475&tt_encode=raw

[TooManyFords]

Just wondering, does the kill switch have to disconnect the alternator? I know it has to disconnect the battery and it has to kill the engine. It should be ok to connect between the fuel pump impact switch and the FPDM (or BAP) for the kill switch part. That will kill the engine by shutting off the fuel pump(s).

Yes, or the alternator will continue to power the car. The alternator output should run directly to the + Battery side of the cutoff switch so when it is thrown, there is nothing left to provide +12v.

[FordNut]

Yes, or the alternator will continue to power the car. The alternator output should run directly to the + Battery side of the cutoff switch so when it is thrown, there is nothing left to provide +12v.

I see. But it can't actually power anything once the fuel is shutoff and the engine dies, stopping the alternator from spinning. But rules are rules...

[-Matt-]

Just wondering, does the kill switch have to disconnect the alternator? I know it has to disconnect the battery and it has to kill the engine. It should be ok to connect between the fuel pump impact switch and the FPDM (or BAP) for the kill switch part. That will kill the engine by shutting off the fuel pump(s).

That could work, but i was reading that buy shutting off the battery before the alternator is shut off it will cause a voltage spike that can damage the alternator.


Use a battery disconnect switch.

http://www.tecknowledgey.com/catalog/default.php?cPath=135&osCsid=0ebb02606832bff61b57284 6316bcd70

http://www.nextag.com/battery-disconnect-switch/products-html

http://shop.ebay.com/items/battery%20disconnect?_dmd=1&_sop=12&rvr_id=&keyword=battery+disconnect&crlp=1900873763_1&MT_ID=475&tt_encode=raw

Sigh.... did you even read my post?


Yes, or the alternator will continue to power the car. The alternator output should run directly to the + Battery side of the cutoff switch so when it is thrown, there is nothing left to provide +12v.

Ok, thats good and all but heres the problem. My battery and disconnect switch is in the trunk. I have a 1/0 gauge wire that runs to the front to a distribution block that goes to the fuse box and alternator. I dont see any way to get the alternator wire back to the disconnect switch without having to run a whole new wire back to it... and who wants an alternator wire that long anyways?


I see. But it can't actually power anything once the fuel is shutoff and the engine dies, stopping the alternator from spinning. But rules are rules...

I read that this isnt good for the motor or the electrical system at all.

[RR|Suki]

There is a relay that painless makes that will solve your problems, go look up rich's posts about his install and the part number should be in there

[-Matt-]

There is a relay that painless makes that will solve your problems, go look up rich's posts about his install and the part number should be in there


I searched and found alot of different threads and info but none of which are what your talking about... link me if you can find it.

[RR|Suki]

I searched and found alot of different threads and info but none of which are what your talking about... link me if you can find it.

I'll try to remember to search after lunch, I dunno if he ever posted that thread over here, I know it's on motorcity though

[TooManyFords]

I see. But it can't actually power anything once the fuel is shutoff and the engine dies, stopping the alternator from spinning. But rules are rules...

I agree, but what if you get a short somewhere and it finds a path back to the fuel pump anyway? There is only one sure way to kill everything, and that is to eliminate the battery and alternator.



Ok, thats good and all but heres the problem. My battery and disconnect switch is in the trunk. I have a 1/0 gauge wire that runs to the front to a distribution block that goes to the fuse box and alternator. I dont see any way to get the alternator wire back to the disconnect switch without having to run a whole new wire back to it... and who wants an alternator wire that long anyways?


Yes, it is a long way back to the cutoff switch, but it is required.

[Pops]

Its just more wire. You can do it in one hour or less.

[-Matt-]

So run 2 lengths of 1/0 gauge? Or run the 1/0 to the alternator then run an additional 4 gauge to the fuse box?

[TooManyFords]

I have 0/1 gauge from the battery to the switch, and from the switch to the main fuse panel under the hood. I ran 4 gauge from the alternator back to the switch.

[-Matt-]

I thought the bigger gauge wire was needed for the alt? I guess i was wrong about that.

So if i hook up the fuse box and the battery to the one side of the battery disconnect switch and the Alternator wire to the other, essentially when the battery disconnect is shut off the power to the alternator will be cut off, causing the car to shut off. It wil still run on battery power though. Now if i do the alternator and fuse box wire to one side and the battery to the other it would cause the alternator to back feed into the fuse box letting the car still run but shut off the battery.

Im still not quite understanding it.

[Pops]

Get the switch and use the directions Matt. You are over thinking this. The switch interups both the Battery and the alt. when it goes to the off position.

[TooManyFords]

http://img.photobucket.com/albums/v244/tepid1/Powerfordummies.jpg

[-Matt-]

Ahhh.... i see now

[massacre]

Awesome diagram

[GetMeMyStogie]

This is probably a dumb idea, and I'm assuming you need this for drag racing, but can you run a shorter serpentine belt for the races, one that doesn't wrap around the alternator? You'd need a good battery, and to shut off all accessories, of course.

[-Matt-]

This is probably a dumb idea, and I'm assuming you need this for drag racing, but can you run a shorter serpentine belt for the races, one that doesn't wrap around the alternator? You'd need a good battery, and to shut off all accessories, of course.


Most true drag cars dont run an alternator

[-Matt-]

What size fuse are you using for the 4 gauge alternator wire? I have a 220amp alt btw.

[DEFYANT]

Do our alts turn off at WOT? I thought they did.

[TooManyFords]

What size fuse are you using for the 4 gauge alternator wire? I have a 220amp alt btw.

Then I would recommend a 300 amp fuse. If you run a trunk mount battery, you want to have a fuse at both ends of the alternator wire. This is because any short in this wire needs to isolate both ends, the battery from the back and the alternator from the front. The fuse should be big enough that normal usage does not blow the fuse. I run a 250 from the alternator and a 300 amp from the battery up to the front of the car. These seem to be fine. The cable from the battery to the front panel need only be fused back by the battery.

[TooManyFords]

Do our alts turn off at WOT? I thought they did.
Yes, if you run the factory regulator and the original PCM. Mine runs all the time. But this thread is about kill switches, Charlie.

BTW, hi!

[-Matt-]

Then I would recommend a 300 amp fuse. If you run a trunk mount battery, you want to have a fuse at both ends of the alternator wire. This is because any short in this wire needs to isolate both ends, the battery from the back and the alternator from the front. The fuse should be big enough that normal usage does not blow the fuse. I run a 250 from the alternator and a 300 amp from the battery up to the front of the car. These seem to be fine. The cable from the battery to the front panel need only be fused back by the battery.

300? where did you get that number?!?

The fuse should be close to the total amperage draw on that certain line. Theres no way running from the alt to the battery exceeds that. (i was planing on running 100 amp fuses on both sides of the 4 gauge and 200 amp breakers on the 0/1 gauge.)

[FordNut]

What size fuse are you using for the 4 gauge alternator wire? I have a 220amp alt btw.

At least the next size bigger, a 250 or 300A

[FordNut]

Then I would recommend a 300 amp fuse. If you run a trunk mount battery, you want to have a fuse at both ends of the alternator wire. This is because any short in this wire needs to isolate both ends, the battery from the back and the alternator from the front. The fuse should be big enough that normal usage does not blow the fuse. I run a 250 from the alternator and a 300 amp from the battery up to the front of the car. These seem to be fine. The cable from the battery to the front panel need only be fused back by the battery.

I'm surprised the 300 amp will carry the starting current.


300? where did you get that number?!?

The fuse should be close to the total amperage draw on that certain line. Theres no way running from the alt to the battery exceeds that. (i was planing on running 100 amp fuses on both sides of the 4 gauge and 200 amp breakers on the 0/1 gauge.)

Way too little.

[TooManyFords]

300? where did you get that number?!?

The fuse should be close to the total amperage draw on that certain line. Theres no way running from the alt to the battery exceeds that. (i was planing on running 100 amp fuses on both sides of the 4 gauge and 200 amp breakers on the 0/1 gauge.)

That's fine, let us know how it works out. To be honest, I've never blown any of my fuses and I may have over-engineered my system. I chose 300 because I wanted to make sure I had enough juice for the starter. Maybe I should look into breakers instead of fuses and see how low I can go.

[GetMeMyStogie]

Most true drag cars dont run an alternator

I was suggesting that, by not running a belt around the alternator, you might be able to avoid the alterterntor-kill-switch rule altogether (if the alternator is not spinning, it's not making power). I don't know if that would get you around the rules or not, but it'd be a low-buck, low-effort way around them if it is legal. Swapping accessory belts is pretty easy on an N/A motor, but it's not something you'd want to do every day - maybe on the weekends.

[TooManyFords]

It would. The only thing they test in the tech area is that when the kill switch is thrown, the car dies. If it doesn't, you don't pass tech.