bubba377

what is the proper way to wire the master cut of switch when you relocate the battery to the rear of the car so that the car shuts off when the switch is turned off.is there a way to do this with a relay to keep from running the alt wire to the back of the car I have the switch mounted and the battery mounted just need to run the wires yet and I am done thank you for your time

p.s. a wiring diagram would be great

IHI

iTrader: (1)

I just recently got mine hooked up like it shoulda been Truth be told, cheapest way will be to run wire from back of alt to battery positive. I've got a 120amp alt. and bought 18' of 4ga welding wire and 2 wire ends for $21.38 that's with tax, and it took all of 30 minutes to run the wire back and make connections and now it works like it waw supposed to when i first put it in. Also charge going to battery is alot better with this set-up too. Literally, everything in my car is electrical and when car was running and I'd hit the switch for the water pump/dual electric fans, it'd drop about 1-1.5V and gauge would stay on 13V, since running this big wire to battery, gauge shows 15V but actually only pushing 14.70 at alt and batt., and now when I hit pump/fans gauge dows not move, so that was also a big plus in my book.

They make shut off switched with alternator wire provisions now too, but even that requires running wire to back of car.

Jason Dammen

Like IHI said make sure it goes to the battery post. What I found out is that if you dont run a seperate wire to the back of the car and just splice it in with main big wire to the starter when the car is running and you shut off the switch, the car will stay running because the alt. is still putting out power and allowing the ignition to stay on. If you get it wired correctlly, when you shut of the switch the car will immeditely shut off. I dont run a relay in my car but it wouldnt be a bad idea. If you wire it directly from the alt. to the battery, the alt. is always powered so if you are going to store the car for a long time you will want to disconnect the battery. Just my two cents.
Later
Jason

SDIF

I dont understand why the rules do not allow you to disconnect the ground from the battery via the switch. By rules I mean SCCA / NASA /etc.

This would solve all the above mentioned issues and would be safer too.

IHI

iTrader: (1)

I would assume that there are many places/items that are seperately ground to chasis so there would always be another route to ground, where as it gets juice from the battery for hot, take away the hot and there's nothing to power.

xpndbl3

iTrader: (5)

exactly. the + lead will kill the engine immediately whereas pulling ground can feedback loop through the alternator and continue supplying power to keep the engine running.

AlkyIROC

The positive cable is just a safety issue. If there wasn't a rule, the negative would do the same thing.

The safety part is in case you're in an accident. If a powered wire gets pinched in some metal, it can cause a short and an electrical fire or some very hot wiring. If the master shutoff kills the positive source, there won't be any electrical fires.

Some of the high end race cars even have an internal control so that the driver can also disconnect the master switch in case there's a problem. Something simple like a cable going back to the master switch or a second master switch. Mount the cable with a Tee handle on the roll bar behind the driver head. He just needs to reach up and pull the cable.

Mentor58

One other good reason to run the output of the Alternator directly to the battery rather than to a seperate terminal on the master switch is that way if the switch is shut off while the engine is running the battery still acts as a sink for the Alt output while it spools down. In theory this does mean that the length of wire connecting the alternator to the battery is ALWAYS hot, but it is legal, and if you were really paranoid about not having that be a fire hazard you could mount a CB at the battery end of that wire, so even if it shorted out, the Breaker would protect the system.

Just A Thought

Steve W

SDIF

Help me understand...

If the ground cable is disconnected at the battery and there are no other connections, how can a "feedback loop" find a ground?

I am not trying to agrue, but if the ground cable is disconnected rather that the + how is this less safe?

The electrons do flow from the negative side of the battery and return to the positive side.

xpndbl3

iTrader: (5)

the alternator will ground into the chassis and continue the flow bypassing the battery ground completely. this is why on older cars you can pull the wire off a battery and the car will continue to run.

blacksheep-1

Here's another thought, in my car, I poneid up the big $$$$ and bought welding cable (fine wire) for both the positive and the negative.
And yes you're right, if you disconnect the ground wire the current will "hunt" another ground source.

SDIF

Thanks,

83 Crossfire TA

iTrader: (2)

Did it really take 18’?

I take it that you guys are ending up with a ground wire that goes straight to the body somewhere, a positive wire that goes to the big stud on the starter solenoid, a smaller positive wire that goes to the “bat” connection on the starter and you eliminate any other wiring to the starter?

What about the sense wire from the alternator, is that still connected to the starter or wherever it goes to in the stock wiring harness? Does this have any negative effects on things when tech inevitably tests your kill switch (the sense wire would see 0* when the circuit is broken by the switch so the regulator would send all the power it get get it’s hands on to the field coils of the alternator through the second wire connected to the “bat” terminal)?

IHI

iTrader: (1)

My battery is in teh rear pass. 1/4 panel and I use a ford solenoid if that helps paint a better picture.

18' since it has bends and turns to make that you lose wire on, I have the ground wire going to the chasis and battery negative.

My alternator has a 10 ga. jumper from the hot on the 2 way spade termial to the battery connection on the back of the alt, then the heavy ga wire goes from back of alternator + to the positive on the battery. Feild wire on the alternator has not been messed with and is still going into the factory harness on that leg of it.

mw66nova

iTrader: (13)

so, i have a 1-wire alternator. can you explain in detail the wiring i would need to relocate my battery with a kill switch? what wires go through the switch? sorry, but i'm really confused now.

IHI

iTrader: (1)

Run that wire from alt directly to the battery positive terminal. Then run a separate wire from the battery positive to the cut off switch.

mw66nova

iTrader: (13)

and then from the switch to the starter?

Free Bird

iTrader: (1)

And that will kill the cars power instantly?

IHI

iTrader: (1)

yes

Bluedeuce

I'm having a problem with my Nova; I have wired in a kill switch (with the battery in the trunk) and I also have a relay. Problem; big power draw and battery goes dead in one day with switch on or off. Your answer does not seem to address the relay. Could you explain how this setup should be wired?

AlkyIROC

The alternator should be wired directly to the battery hot and doesn't get affected by the master switch. If your battery is still going dead, you may have a bad alternator or something else is hooked to that hot circuit on the alternator.

I just changed my alternator last week after it failed. When I was hooking it back up, I realized I had my field wire hooked up to my master power switch inside the car. Not really a big problem but I have the master switch on between rounds to have power for the water pump and fan to cool the engine down. I rewired the field wire so it would only get power when the ignition switch is turned on. This worked better until I realized I couldn't turn the car off without turning the rear master switch off. A simple rewire with a relay fixed that problem. Ignition switch now turns on a relay. The relay takes power from the master switch side to feed the field wire. If the master switch on the dash or at the rear is turned off or the ignition switch is turned off, power is disconnected from the field wire by the relay and it won't keep the ignition powered up and the car shuts off.

Bluedeuce

I just got back to the forums. Thank you for the information. I have the master xwitch wired now and I think it is right. It cuts the engine off as it should, and the relay doesn't get hot with the switch off. The relay still gets hot with the switch on, but I think that is normal. It just bothered me since this is a street car (mostly) and it (the relay) stays hot while I drive. Painless Performance says that is normal. I just have to remember to shut the switch off if the car is going to sit for a few days or the battery will be dead!

CamarosRUS

Is everyone running 2 or 4 post battery disconnect switches WITH alternators?

I'm trying to figure out which one I need and if running a kill switch with an alternator will either fry the switch or do something screwy with my volts...

xpndbl3

iTrader: (5)

2 post switch doesn't fry anything no different than turning the key off and telling the alternator to shut down.

IHI

iTrader: (1)

2 post

trick is to run a completely new alternator output wire from the alternator directly to the battery positive...you do this and your done.

Do yourelf a huge favor and run a heavy guage wire for the alt output too. I had the factory 10ga and my volt guage was always low when night driving and everything electrical going full tilt. i swapped it out for 4ga and BAM, HUGE increase in charging and available voltage from the battery...my volt guage went from 13.5 to 15 with only the larger guage wire upgrade, fans ran better, lights were brighter, fuel pump sounded better, etc....

CamarosRUS

Thanks.

IHI, I've read all about your setup. I have read (but will go this route anyway) that running the alt lead directly to the battery can hurt the battery/alt when the kill switch is flipped. Also, seen that the 2 posts switches are NOT for use with an alternator


When finished, I should (hopefully) see amazing voltage:
1/0 + from battery to switch and switch to distro block on passenger firewall.
1/0 + from distro to starter.
1/0 GND from battery to frame.
4 ga GND from battery to passenger head.
4 ga GND strap from passenger head to frame in engine bay.
AND 4 ga alternator charging wire from alt output to wherever!!!


I am running the el cheapo 20 amp continuous/125 amp surge Summit switch and feel this is a huge issue in all of my electrical gremlins. I plan to get the 300/2000 amp Moroso 4 pole switch anyway to eliminate this bottle neck (and if I need to rewire the setup to use the 4 posts down the road).


Moroso recommended this Painless relay http://store.summitracing.com/partde...-50105&FROM=MG because the smaller posts are only rated at 20 amps. Not having it could still fry their Super Duty (300/2000 amp) switch.


What amperage is your switch rated at IHI?


BTW...LOVE the vid in your sig

xpndbl3

iTrader: (5)

How is moroso stating that their 300amp continuous switch would be fried if a cars electrical system never runs that many amps, and especially not 2000 peak amps.

IHI

iTrader: (1)

My switch is just a standard 200 amp unit, nothing fancy. I guess after 7 years on the same battery and everything is still working just fine i'm lucky since this set up has'nt hurt my electrical service...never heard that one before..but am willing to bet it might have been conjured up by a salesman somewhere trying to upsell the multi post on/off switch.

I would'nt even bother running a ground from the battery to the passenger side head, waste of money. I ran a 2ga ground wire from battery to where the plate for my cage is welded to the body. Then up in the engine bay i have solid motor mounts, a 2ga ground wire from the chasis to the motor mount, and then another ground strap (woven type) from the firewall to the head...like i said, everything works great, and my lights dont even dim when i'm jamming the tunes either

CamarosRUS

Well I told him I was already going to run the 4 post switch. I'm assuming he figured if I hooked up the alt charging wire directly to the smaller 20 amp posts it would fry them. I don't know if Painless and Moroso are sister companies but if they are it would explain a little more.


I think I will go with the 300/2000 amp 4 post Moroso switch and run the alt lead directly to the battery, as suggested. If it doesn't work out I can run the field wire and respective jumper wire to the smaller posts and if it still doesn't cooperate I can spend $90 on the damn Painless relay.

Thanks for the help you guys.


BTW...had the 4 ga wire laying around and you can never have too many grounds, especially direct grounds to the motor

xpndbl3

iTrader: (5)

why the 4 post over the 2 post that everyone I know runs?

Shagwell

If you run a large pos to the alt directly from the bat you have just eliminated part of the safety aspect of the cut-off switch. Although shutting the master off will "kill" everything electrical in the car, you still have a live 4+ gauge pos wire running the length of the car that could be pinched somewhere. - Hence the 4 post switch that has a seperate post for the alt pos to feed through, although if it's only rated at 20 amp, you would need some sort of a relay or continuous duty solenoid to utilize it. (guessing the painless, as reccomended)

If you utilize a triggered alt, you could wire it as Stephen 87 IROC explained. That way doesn't require the extra length of large cable to the bat, but will still "kill" all electrical devices when the master is clicked off. With a one-wire alt I believe the 4-post switch is require to be legal, and if the small posts are only rated for 20amp, you would need a relay/solenoid to handle any decent alt.

CamarosRUS

I'm aware that the alt lead will always be live at this point but it is still legal and I do not want to spend $90 on a damn relay. I may in the future run the field wire from the alt to the switch but will have to live with this for now. If the field wire idea does not pan out then I will bite the bullet and buy the Painless relay. However, I just got news yesterday I will more than likely be moving for a new job shortly after the first of the year so my car is going to have to sit for god knows how much longer...

xpndbl3...I want to run the 4 post in case I need/want to wire things differently in the future. Also, I need to stick with that exact design due to how I drilled the hole and mounted the switch and I wanted something rated at 300 continuous amps or more. This was the only one.