Battery cutoff switch and msd, car wont die

Battery cutoff switch and msd, car wont die - 08/02/13 01:31 AM

How do you wire an msd box with a battery cut off switch and have the car shut off when the cutoff switch is flipped off. When I bought the car the msd box heavy red wire was hooked to the back of the alternator and the cutoff switch would kill the car. The msd instructions say not to hook it to the alt, I figured that is why the original box I had died. So I wired it to the off/ disconnected side of the cutoff switch and the switch wont kill the car. My car doesn't have the stock wiring but it is wired battery to the cutoff switch and everything comes off of the disconnect side of the cutoff switch. Any ideas would be great. I have tried msd's instructions of using a 4 pin ballast resister on the small red wire on the box and it didn't help. I also tried the msd's big wire to the battery directly and it did help. Im just afraid to rewire it to the back of the alt and have another box fail. If it matter's its a 2 pole cutoff switch.

Posted By: Plymouth340

Re: Battery cutoff switch and msd, car wont die - 08/02/13 01:34 AM

you need to run the alt wire back to the cut off switch.

Posted By: 70AARcuda

Re: Battery cutoff switch and msd, car wont die - 08/02/13 01:48 AM

Quote:

you need to run the alt wire back to the cut off switch.

the battery side of the master cut off switch...

Posted By: Jeepmon

Re: Battery cutoff switch and msd, car wont die - 08/02/13 02:12 AM

The alt wire and the battery wire needs to be on the same side of the cut off switch...

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/02/13 02:51 AM

I have tried both sides of the cutoff switch and it wont die. The alt is hooked to the disconnect side. Are you saying the alt should be wired to the battery side of the switch? I thought the cutoff switch should kill all power to the car.

Posted By: 70AARcuda

Re: Battery cutoff switch and msd, car wont die - 08/02/13 04:31 AM

Quote:

I have tried both sides of the cutoff switch and it wont die. The alt is hooked to the disconnect side. Are you saying the alt should be wired to the battery side of the switch? I thought the cutoff switch should kill all power to the car.

it wont...

been there...done that...

Posted By: MR_P_BODY

Re: Battery cutoff switch and msd, car wont die - 08/02/13 04:36 AM

Quote:

I have tried both sides of the cutoff switch and it wont die. The alt is hooked to the disconnect side. Are you saying the alt should be wired to the battery side of the switch? I thought the cutoff switch should kill all power to the car.

All that switch is doing is cutting the battery source...
just like if you disconnect the battery in a production
car.. it continues to run... the big alt wire need
to go to the master shut off on the battery side of
the switch

Posted By: Jeepmon

Re: Battery cutoff switch and msd, car wont die - 08/02/13 05:10 AM

Quote:

Quote:

I have tried both sides of the cutoff switch and it wont die. The alt is hooked to the disconnect side. Are you saying the alt should be wired to the battery side of the switch? I thought the cutoff switch should kill all power to the car.

All that switch is doing is cutting the battery source...
just like if you disconnect the battery in a production
car.. it continues to run... the big alt wire need
to go to the master shut off on the battery side of
the switch

Posted By: 6bblFLASH

Re: Battery cutoff switch and msd, car wont die - 08/02/13 07:33 AM

I put a diode in my field wire,that fixed mine

Posted By: 70HemiGTX

Re: Battery cutoff switch and msd, car wont die - 08/02/13 07:46 AM

I ran a wire from my battery disconnect to a relay that powers (red or hot wire) my MSD control box. When I turn the switch off the relay is truned off, thus killing the MSD box. Just like turning the key off and a lot less amperage going though the disconnect switch. Very easy to do.

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/02/13 12:00 PM

What gauge wire should I run for the alt, Its a 120 amp cs130. Right now its hooked to my starter wire which is huge.

Posted By: Jeepmon

Re: Battery cutoff switch and msd, car wont die - 08/02/13 11:47 PM

Quote:

What gauge wire should I run for the alt, Its a 120 amp cs130. Right now its hooked to my starter wire which is huge.

This is the tricky part.. per the spec's on a 120 amp alt, you need some stupid size wire like 4 gauge... but it will (almost) never be putting out a solid 120 amps..

So the simple answer will be the bigger, the better.. Me personally, I would go with a 10 gauge stranded wire... or even 8 gauge... if you can... That'll protect you for up to 50 and 75 amps..

Posted By: 70HemiGTX

Re: Battery cutoff switch and msd, car wont die - 08/03/13 05:12 AM

If you get a disconnect switch with 4 posts you can run the MSD cut off through it. I'll look at how I have mine wired tomorrow. I don't exactly remember how I did it. But it is much safer than running a heavy alternator wire the full length of the car and back!

Posted By: 340B5

Re: Battery cutoff switch and msd, car wont die - 08/03/13 06:09 AM

Quote:

I put a diode in my field wire,that fixed mine

Good idea

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/03/13 01:56 PM

Quote:

Quote:

I put a diode in my field wire,that fixed mine

Good idea

I may try this today. I have 1 that came with the msd box. Not sure if it will work ok with the resister but I will give it a try. I like the idea there is no power in the car with the disconnect switch off.If this doesn't work I may try running the msd off a relay.

Posted By: MR_P_BODY

Re: Battery cutoff switch and msd, car wont die - 08/03/13 02:28 PM

Quote:

Quote:

Quote:

I put a diode in my field wire,that fixed mine

Good idea

I may try this today. I have 1 that came with the msd box. Not sure if it will work ok with the resister but I will give it a try. I like the idea there is no power in the car with the disconnect switch off.If this doesn't work I may try running the msd off a relay.

On the 4 post master.. I dont know how many amps it
can handle but if you ran the field wire to the small
post it will do the same(any way to turn off the alt..
but if you isolate the large alt hot lead I have never
seen a issue (using isolated clamps to hold it on
the frame)... I prefer to do it the easiest way possible
because if it brakes down at the track you want to
be able to fix it easy.. thats why I dont run a diode
or a solenoid to kill it... the old KISS system..
if you wanted you could run a 100 amp fuse at each
end of the alt lead(1 at each end would cover a short
anywhere on that line).... JMO

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/03/13 03:53 PM

The diode idea didnt work I just tried it. And a solenoid wont either do to it needing a power loss to kick it off and nothing losses power with the alt powering it. I guess I will just run the alt wire and msd directly to the bat itself. I do like the idea of fuses on both sides of the alt line. And for what it's worth I tried the msd on the back of the alt and with the new box it didn't die either. Maybe because it's digital and not analog like the old box. I don't know why with the old box it would kill the car.

Posted By: RobX4406

Re: Battery cutoff switch and msd, car wont die - 08/03/13 04:24 PM

How many wires are connected to the alt output terminal and where do they go.

If you left the factory wire that goes there, disconnect that and see if it kills it.

Posted By: MR_P_BODY

Re: Battery cutoff switch and msd, car wont die - 08/03/13 04:32 PM

Quote:

The diode idea didnt work I just tried it. And a solenoid wont either do to it needing a power loss to kick it off and nothing losses power with the alt powering it. I guess I will just run the alt wire and msd directly to the bat itself. I do like the idea of fuses on both sides of the alt line. And for what it's worth I tried the msd on the back of the alt and with the new box it didn't die either. Maybe because it's digital and not analog like the old box. I don't know why with the old box it would kill the car.

Is your alt a single wire(hot only) or is it using
a external regulator.. if it has a external regulator
you have 2 field wires... one is a sense wire and
the other is keyed hot.. if you break the keyed hot
lead you then kill the alt... here is a simple wiring
diagram of how the system works

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/03/13 04:49 PM

My alt is wired this way
S - connect this right to the "+" on the Alt. with a ring terminal
F - Not needed
L - Connect to 12V source with a 3-4 Watt bulb in the circuit (see web page on CS130 repair) I have a resister instead of the bulb
P - Not used
And the big Wire go's to my starter and back to the disconnected side of my cutoff switch.
Also on the stud the alt is 1 wire that go's to the starter, 1 wire that jump's the s terminal to the stud, and I have my cooling fans wired to it.

The alt is internally regulated GM CS130
I have no stock wiring in the car, The person I bought the car from wired it himself. The whole car is wired off the disconnect side of the cutoff switch.

Posted By: 11secdart

Re: Battery cutoff switch and msd, car wont die - 08/03/13 05:27 PM

I had the same problem my Dart would`t shut off at the switch, I ran a new wire directly from the alternator to two relays to the switch and problem solved, it also starts easier and the battery does`t need charging as often as it used too.

Posted By: 64hemi330sedan

Re: Battery cutoff switch and msd, car wont die - 08/03/13 05:45 PM

Quote:

The diode idea didnt work I just tried it. And a solenoid wont either do to it needing a power loss to kick it off and nothing losses power with the alt powering it. I guess I will just run the alt wire and msd directly to the bat itself. I do like the idea of fuses on both sides of the alt line. And for what it's worth I tried the msd on the back of the alt and with the new box it didn't die either. Maybe because it's digital and not analog like the old box. I don't know why with the old box it would kill the car.

the diode will only flow power one way.turn it around and see if that will do it.if its wired the wrong way it wont work.

Posted By: challengermike

Re: Battery cutoff switch and msd, car wont die - 08/03/13 06:02 PM

Quote:

Quote:

The diode idea didnt work I just tried it. And a solenoid wont either do to it needing a power loss to kick it off and nothing losses power with the alt powering it. I guess I will just run the alt wire and msd directly to the bat itself. I do like the idea of fuses on both sides of the alt line. And for what it's worth I tried the msd on the back of the alt and with the new box it didn't die either. Maybe because it's digital and not analog like the old box. I don't know why with the old box it would kill the car.

the diode will only flow power one way.turn it around and see if that will do it.if its wired the wrong way it wont work.

I checked it before I put it on. I had it so the power would only flow to the alt. If I flipped it other way my alt wouldn't charge. And it was charging when it was on there. I do understand now why a diode wont work. The power isn't going backwards but the way I have it wired its making a loop that keeps everything powered. Im sure the only way to cured this is to wire the alt and msd to the pos side of the battery like mr p body said.

Posted By: 64hemi330sedan

Re: Battery cutoff switch and msd, car wont die - 08/03/13 07:08 PM

Quote:

Quote:

Quote:

The diode idea didnt work I just tried it. And a solenoid wont either do to it needing a power loss to kick it off and nothing losses power with the alt powering it. I guess I will just run the alt wire and msd directly to the bat itself. I do like the idea of fuses on both sides of the alt line. And for what it's worth I tried the msd on the back of the alt and with the new box it didn't die either. Maybe because it's digital and not analog like the old box. I don't know why with the old box it would kill the car.

the diode will only flow power one way.turn it around and see if that will do it.if its wired the wrong way it wont work.

I checked it before I put it on. I had it so the power would only flow to the alt. If I flipped it other way my alt wouldn't charge. And it was charging when it was on there. I do understand now why a diode wont work. The power isn't going backwards but the way I have it wired its making a loop that keeps everything powered. Im sure the only way to cured this is to wire the alt and msd to the pos side of the battery like mr p body said.