All,
I’m not very good with electrical at all.
What I’m trying to figure out is wiring for stock alternator/voltage regulator with MSD 6al AND how to cut power to it with the master kill switch as I have the battery in the trunk.
I have the MSD wired up per instructions.
I completely lose the ballast resistor, correct?

I’ve searched on here, can’t find exactly what I’m looking for, so I thought I’d come to the experts for advice.

Thanks in advance all.
Pic is my Demon, getting excited as I’ve owned it since ’83 when I was 15.

You need the kill switch to be able to shut the current off to the car so that means the big charge wire from the alternator needs to be routed to the battery side of the kill switch and then routed back from the switched side of that switch back to the starter relay feeding (charging) the battery off of the starter. I would replace the stock battery wire with a #8 or maybe even a #6 gauge wire depending on the amperage the alternator makes, 35 amp for 35 amps,or # 6-gauge for 60+ amps. The increase length of the charging wire comes into play so a lot bigger is better than a tiny bit to small
Have fun

Yes, lose the ballast resistor.

One wire alternator will make life much easier.

The fat red wire you can run to any location that is hot, even the alt output stud if you want. It is nothing but a feed for the box. Although it may be better to pull a larger wire forward (noise buffering from battery) from the battery/downstream side of switch to a bus point.

The "important" wire is the small red trigger wire. That wire needs to be on your downstream side of the cut off switch. Cut off thrown, box goes dead, no signal. Putting the fat red on the same side also cuts of operating current.

Just depends on the approach you wish to apply.

I'm thinking about that.....
Already spent $40 to have the alternator taken apart an press the March Pulley on, I'm trying to be cost effective (Not really cheap) but want it to be working correctly.
Is the Painless 50105 Alternator Shutdown Relay necessary to cut all power to it?

Thanks all for the assistance......

Wally.

CD relays are available that do the job for around $40 or less. If you want to kill that line when the cutoff is thrown.

I use Cole Hersee CD relays

Cab, definitely appreciate your 2¢!
So can this be done without a relay?
As I admitted before, wiring is not my specialty, so I just can’t picture it.
I’ve been looking online for a diagram, got nothing.
I know once I understand it, it’ll smack me in the face…..
Thanks again all!

Normally on most later model years, from 1962 and up to 1973 Mopar's the big red wire from the alternator is routed to the starter relay and then down to the big positive lead from the battery on the starter solenoid, this routs the current made by the alternator to the battery.
What you need to do is to make sure the car will not run with the battery cut off switch turned off, by routing the feed to the battery from the alternator back to the cutoff switch you are isolating the current to the rest of the car when it is turned off You are creating a switch that isolates the alternator feed from the rest of the car when turned off

Here is the best solution that I found for doing this: https://www.summitracing.com/parts/mor-74107
The instruction sheet is on the site to show how to wire it in. There may be cheaper versions of solenoids, but I went this route knowing that Moroso made this for doing exactly what I wanted to do.

I have the Painless version in my Dart.

Why buy two parts when one will do the job?
Or are you only using one relay with a switch?

Sorry for the delayed response Cab... But just saw the question. It has been a while since i wired mine, but what I remember is most switches aren't rated to handle the voltage of the alternator going through them (?) So, the external 250 continuous duty solenoid is needed to support the alternator, and the solenoid gets wired to the switch to shut down the alternator to the battery, the switch also kills the battery feed to the rest of the car.

The unrealized problem in wiring for a trunk battery is with the car running, you have two positive sources running the car. One from the battery, and one from the alternator. If you wire it such that it turns off the battery, the alternator continues to run and power the system*. So, you either have to cut the field power to the alternator to turn it off (which requires either a 4 pole cutoff switch or a relay/solenoid) or wire the alternator output to the + battery making the car run on a single positive source.

I might add also that if that alternator output has any other connection to anyplace else other than the + battery you run into the dual + supply again.

Many people wire it wrong as in the first instance, but turning off the switch "works" at idle as the power draw is greater than can be supplied by the slow speed alternator. But note the asterisk below. More than one person has had tech inspect the cutoff at high idle and the car shuts off due to fried "stuff". ending the racing day right there in tech. Seen it, not on my stuff.


*Running the car with the battery cut out can allow the alternator to put out way too much power. I've measured 20 VDC at idle, but not for long, the MSD will die.

This is exactly what I’m dealing with at the moment…….
With the relay I have no problem wiring up as per the attached diagram from painless.
The main question is now - what to do with the black wire that was on the post from the original wiring harness?
I’m thinking undo it from the bulkhead connector under the dash and run it to a 12v source?

Thanks all for the input!

What you are missing in that diagram is power to the rest of the car. That can come from the starter battery wire to the start relay as in the original wiring, or some other wiring from the down stream from cutout switch. The way that diagram is, you don't really need the relay, it could be bypassed.

As far as original wire (depending on the year) it went through the amp meter in the dash, then back to the battery via the post on the start relay. Just remove it all together. BTW, you cannot use the amp meter with this wiring.

It seems that this alternator to disconnect switch situation is getting way overthought, injecting too many new variables into the mix. Actual time required for protection is being overlooked. All these switch related solutions rely on driver or track crew recognition and appropriate response to operate. Not a good situation in emergency. All that is needed in the B+(output) cable between the alternator and the battery side of the master diconnect switch is an AMG or AMI 100 or 125 amp slow-blow fuse. If the alternator or its charge wire becomes shorted to ground this fuse will do it's job in seconds, much quicker and more reliable than any human interaction, which I think is actually the primary reason for this circuit in the first place. It saves using the master disconnect switch to turn off the energizing coils for soleniod based systems, when parked. Stored vehicles should always have the negative battery terminal disconnected.With a bolted terminal style fuse arrangement there are no moving parts to wear out or fail on race day. The alterntor and it's charge circuit are then protected from a direct short 24/7 even if the negative cable isn't disconnected when parked. So many high end cars are manufactured this way. Hope this helps. Also, this fuse should be as close to the disconnect B+ terminal as possible to protect the wire from shorting too. Bill

Cab, here is an off the wall question. If you are not running an alternator, can you get rid of the thick wire going from the starter relay down to the starter solenoid, or does this also serve another purpose? As I was rewiring mine back up I wondered why that wire was there, since it seemed redundant because the starter has a heavy wire directly to the battery. Just curious.

Mopar used that big black, some are red, wire from the battery post on the solenoid to feed the rest of the car electricidal circuits off of the starter relay: scope:

Cab, your right. That makes sense. Now that I have everything run through my own switches, which go directly to the battery, I can likely delete that wire as well. Just trying to keep things as simple as possible. I have seen some of those switches with a ton of things run to them.