Master electrical disconnect switch wiring question

[chargerfreak]

First let me thank anyone who might be reading this that has helped with my other problems. You guys are awesome!
Here's what's up. I'm mounting my battery in the trunk and as NHRA mandated am installing a disconnect switch on the back of the car. I have a '71 Charger w/ 383 so it has the remote starter solenoid. In the current issue of Mopar Muscle they go through this very installation, but on an A body car that apparently doesn't use a remote solenoid. Also they say the instructions that came with their disconnect switch didn't actually work. They came up with their own wiring plan. The Taylor Vertex disconnect instructions I have show something totally different than either of the diagrams that Mopar Muscle detailed. Whew! Does anyone out there know the proper way to wire this switch taking into mind the remote solenoid? I would like to do this correctly the first time. If anyone knew how I could a hold of an actual diagram that would be awesome. If not, detailed instructions would be great to. Like everything else on the car this is my first time doing anything like this so don't be afraid to treat me like a beginner.
Thank much, Ben

[jelsr]

I think we have a terminology problem here. Your 383 Charger did not have a remote solenoid in OEM form, it's a starter relay. Kinda the same but different? It's a small recangular box with large and small terminals, sits on the driver side inner fender, and the positive battery cable hooks to it. The actual solenoid is on the starter. The new long battery cable will go to the same terminal on the relay that the original cable went to. The disconnect will simply provide a method of disconnecting the battery from outside the car for safety purposes. Other than cable length and disconnect switch the stock wiring diagram will work. The original positive cable may be long enough to go from battery to switch, then the new long cable from switch to relay. Alway install the ground cable last!

[Dennis Jokela]

First off Chrysler does not use a remote solenoid. They have a starter relay either mounted on the firewall or inner fender panel.

I wired mine the easiest way that I could figure out. I used a -0 cable run from the big lug on the starter to one side of the cut off switch. The other side of the switch goes to the +terminal of the battery.

The - terminal of the battery is grounded in the trunk. I used the existing + battery cable as a wire from the big lug on the starter to the big lug on the starter relay.

I ran a 10 guage wire from a field wire to the rear of the car to the kill switch and back to the alternator. By switching the field wire of the alternator the engine will die when the kill switch is turned off.

I hope this is of some use to you.

Dennis J.

[chargerfreak]

First, thanks for the info. You are giving me two ways to do this so I assume both will work??? From what I read in Mopar muscle it sounds like Dennis' way will work, and Jesler's method seems like it should work, but once Mopar Muscle tried it, it didn't for some reason. Jesler's way sounds much easier but....??????

Dennis - You talk about running a "field wire" from the back of the car. What is a field wire, and if there are options, what is the best place to run it from? Is this one of the wires on the alternator? If so which one, and if I run it back to the kill switch - to which terminal? Then you said run a wire from the alternator back to the kill. Again, from Exactly where and to which terminal on the kill. Also, if at all possible you could describe in detail as if I'm looking at the alternator terminals which ones you mean. Remember, I'm a beginner. The alternator is a three wire type.

Again, thanks for the help. This message board and it's members are LIFE SAVOR!!!

Ben

[Dennis Jokela]

your three wire alternator has a large single wire, which is the hot wire. It also has two wires which are the field wires.

The easiest way is to remove one of the field wires, and make up a 10guage wire from the terminal on the alt to the same terminal that the + cable is connected to the kill switch. make up another wire from the same +cable on the kill switch. run that wire back to the alt and hook it to the wire that you removed from the alternator.

This will allow the engine to die when the kill switch is turned off.

I have had good luck with this system.

Dennis J.

PS It does not matter which field wire you use.

[chargerfreak]

Hey Dennis,
Just one more little question. Mopar Muscle had recommended using 8 guage wire, so I go all over town and finally find that guage in the length I need. You had said to use 10 guage, which looks closer to what the guage of the field wires are. Is it ok for me to use the 8 guage that I bought? Is there a problem with running the larger guage off the thinner guage field wire? Just for future use is there any danger in going from thinner to thicker wire in other applications as well? I know not to go from large to small, but I was wondering if it was ok the other way around.
Thanks again,
Ben

[creative1]

as far as the 8 gauge wire goes, you can use it, but you dont really need it. for the field, i doubt that even 10 gauge is necessary... 12 would be plenty big, as the original field wires are only 16 gauge, and they arent carrying more than about 2.5 amps. you DO have to either interrupt the field or the output with the kill switch, though, or it wont work. the field is the easiest as there isnt a lot of current there.

anytime you splice or replace or lengthen a wire, it does no harm to use a larger wire (smaller gauge#), but you dont want to use a smaller wire to replace a larger wire. lots of reasons, but bottom line is that a smaller wire will overheat, if not burn out. also, any time you lengthen a wire, it is also advisable to increase the wire size because a long wire of the same size has added resistance, which will cause a voltage loss. the larger wire minimizes this loss. how much larger you need to go depends on the length of the needed wire. and dont be fooled by the size of the insulation on the wires...just because a wire looks big doesnt mean that it is adequate to do the job.

one thing that you DO have to watch for, though, is fusable links. they LOOK like wires, but arent. they are really fuses, and like fuses, replacing a small one with a large one is like using an oversized fuse... and this is dangerous.

[Dennis Jokela]

Creative, answered the question much better than I could. There is no problem using the larger wire. I used 10 guage because I had it.

You are well on your way, have fun

Dennis J.

[dirty dan]

Originally posted by jelsr
I think we have a terminology problem here. Your 383 Charger did not have a remote solenoid in OEM form, it's a starter relay. Kinda the same but different? It's a small recangular box with large and small terminals, sits on the driver side inner fender, and the positive battery cable hooks to it. The actual solenoid is on the starter. The new long battery cable will go to the same terminal on the relay that the original cable went to. The disconnect will simply provide a method of disconnecting the battery from outside the car for safety purposes. Other than cable length and disconnect switch the stock wiring diagram will work. The original positive cable may be long enough to go from battery to switch, then the new long cable from switch to relay. Alway install the ground cable last!

This is the proper installation process.
This swich is ment to disconect ((ALL)) power quickly and completly from outside the car.

[chargerfreak]

Ok. So Dirty Dan brings up an interesting point here. Not only do I need to kill the engine, but I will be running an electric fuel pump so I need the entire electrical system to shut down with the kill switch. It sounds like the "field wire" method will only kill the engine - not everything. Here's where I get confused - and I'm thinking it's because of the way the battery was wired when I bought the car was kind of funky. Here's how it was wired when I disconnected everything:
There was the 2 guage positive wire going from the large terminal on the starter to the battery - no problem. Then there was a smaller wire going from the other, smaller post on the starter, to the small post at the bottom of the relay. Finally from a small post near the top of the relay another wire went back to the positive side of the Battery. I hope this all makes sense.
It sounds like Jesler is saying I simply need to run the 2 gauge wire from the battery to the kill switch to the relay. Then another wire from the relay to the starter. That's a lot less wires than what I described as originally being on the car. Did the guy I bought this from have this thing completely mickey moused or am I missing something here? There is still that small post on the starter...do I need to run a smaller wire from there to the now vacant post on the relay??? I'm thinking that's going to the ignition - key in the car??? I hope I don't sound to stupid here. There's been a lot of info, and just when I was sure I had it Dirty Dan brings up the excellent point that all electric needs to shut down.
Thanks much. Ben

[dirty dan]

Originally posted by chargerfreak
Ok. So Dirty Dan brings up an interesting point here. Not only do I need to kill the engine, but I will be running an electric fuel pump so I need the entire electrical system to shut down with the kill switch.

Hey ben
Your right on target here.
I don't know exactly what you wireing arangment is.
I know how mother mopar wired it.
But chances are that was many wire splices ago.
So here is the BIG word if.
If every thing is currently working don't fix it.
Now assumeing all is well with the current wireing arangement.
It would be very simple to relocate the battary to the trunk.
As mentioned befor simply use your old poss' cable or something a little heavier to run from the pos battary post to the cut off switch.
Now leaveing the switch with a good heavy gage wire go directly to the large post on the starter.
For this I like to use old welding leads or something close to that size.
At this point reffer back to the wireing arangement you had to start with.
((IF)) you had any other wires that went to the battary then these to should be conected to the large post on the starter.
From the factory there was one that went to the battery along with the main heavy cable.
After completeing these things you should have exactly what you started with,exept the bat will be in the trunk and you will have
a properly functioning kill switch.
Just an added note.
When installing the cable from the switch to the starter,Be sure to:
(A) make sure it is not near the exhaust system.
(B)make sure the cable is tied up securely to the car.
(C) last but very much not least.
Any spot that may rub or scrape or even viberate a hole in the cable insalation.(These spots are dangerous)
And should be surounded with a peice of old heater hose to prevent shorts.
Hope it helps

[The Dartman]

... and I thought I knew all about this setup.

Everything I've read, including some other posts on this subject, state that to have a functioning "whole car" cutoff switch that the positive (charging) wire from the alternator must be run in 10 gauge from the alternator to the positive side of the battery before the master switch.

This prohibits a charging alternator to power a car at all, yet charges the battery as intended.

I wouldn't think that running a field wire back to the cutoff switch would accomplish the same thing since the car would be supplied by power by the alternator charge line still (at least for a short time). I run an alternator cutoff switch while racing to get around this until I can properly wire the car.

I did say I was confused....

Dartman

[creative1]

removing the field current from the alternator will effectively stop it from charging on a mopar. i dont think it does for chebbies with an internal regulator, though, which may be why the stipulation for the 10 gauge wire from the alt output. and yes, there would be a time lag there... there would be no matter how it was wired. it is the length of time it takes the electricity to travel from the switch to the alternator, and electricity travels at 186,000 MILES per second... so how long to travel 20 feet?

[Dennis Jokela]

Ben:

Switching the field wire and the +battery cable will kill all power.

Dennis J.

[chargerfreak]

Creative - You're saying that the field wire method does kill the engine. I think we all agree on that. But does it kill the entire system - electric fuel pump and anything else? And I was just thinking, between the field wire and and the large guage wire that is going to the starter - when I turn the master disconnect off, isn't that going to kill everything? I mean you've got this big switch between those wires and the actual battery - it seems like when you flip that switch you're absolutely killing the battery. My head is swimming with all of this.

Also, you've got two posts on the starter - one big - one little. I know the big post is positive. Is the small terminal positive as well? Is it just an additional post for the relay or????? I feel like if I knew what every wire and post was there to do I could really figure this out with you guys.

And Dirty Dan - I'm usually right there with you on the "if ain't broke don't fix it", but I'm really trying to make this car as logical, simple, and beautifully put together as possible. For that reason - if the wiring was mickey moused when I removed everything I'd really like to put it back together just right, especially with the relocation of the battery and adding the kill. Everything I've changed, fixed, or modified on this car, I've really taken my time and done it right. I want to do this wiring correctly the first time.

As always, thanks to everyone who's been taking part in this discussion.

Ben

[creative1]

no... what i am trying to say is that to kill the entire electrical system the charging circuit must also be killed. the alternator can energize itself under certain conditions, and that will allow the engine to continue to run. that is why either the field or the output from the alternator must be interrupted, in ADDITION to the main cable to the starter. i would choose to interrupt the field rather than the output for 2 reasons: it is just as effective as interrupting the output; and it is more economical (and easier to run the wires (maybe safer, too) ) to run 20 feet of #12 wire than to run 20' of #8 wire. with around 70 amps at full load, i would lean toward #6, myself.

[The Dartman]

Creative is right about that fact that a charging alternator WILL run a car even if the battery is disconnected. But, you usually fry something. Not a good idea. I had a tech at the local track make me start the car and then try to hit the disconnect to shut me down. The car ran for about a minute and pop! something let go in the alternator.

It is a known fact that the field wire when disconnected will keep an alternator from charging - this is how most Mopar guys rig an alternator disconnect for those couple extra HP. What I don't know is that a field wire is 12 volts all the time and can be be connected to the "after switch" positive lead to the battery. Unless I'm mistaken, the only cutoff switches I've seen are only for one circuit (mine is). I assumed that the field wire is switched by the ignition in a stock setup, so by adding a wire to go back to the battery, aren't we effectively powering an alternator all the time? Does this cause 12 volt draw or other problems on a street car that may have the master power on for several days or weeks at a time.

I guess my main question is how the field wire is switched in your layout? Part of the master cutoff? A switch with dual fields?

I am getting ready to do this myself since I will be running NHRA in September for the first time in about 6 years, and they seem to grill the cars through tech a little more than IHRA. I would like to use the field wire but I can't visualize how it could work correctly. Everything else I have read shows the main charging wire going back to the battery before the switch, effectively putting the charge and battery BOTH before the switch.

Dartman

[chargerfreak]

Dennis: What do you think about what Dartman is saying? I'm thinking I should go with your wiring setup - the one you said you've had good luck with. Did you do what you recommended on a street driven car, or a drag only car? I'm building my Charger for street/strip use. Any thoughts on what he's saying about this method being bad for the alternator, or about the car continuing to run for "a minute" even after the switch is thrown? Did you ever have that experience?
Thanks, Ben

[The Dartman]

I want to clarify that I'm not sure how the disconnect would connect to an existing master cutoff switch, unless it had two circuits. On a running car, both sides of a master cutoff switch will have 12 volts DC - one with battery voltage, the other with alternator generated 12 volts DC (or more).

I would rather run the thinner wire (cheaper, easier) to the back myself, but I don't understand exactly how they are wiring it up.

Dartman

PS - It is my understanding that the voltage regulator really regualates the voltage of the battery. Without a battery in the picture (running on alternator voltage alone) it is possible that the alternator could cause voltage spikes that can take out certain electronic devices in a car. In my case the alternator itself. Someone else could clarify this much better for us....

[dirty dan]

Hey Guy's
6 of one and 1/2 dozen ofthe other.
My experiance with cut off switches does not include cars with altenaters.
How ever if I were to run an altenator on a race care I can see were an altenator cut off would also be required.
OR I would simple unplug the voltage regulator for the afternoon.
Dart man Both will be required to get through tech.

[Dennis Jokela]

Ben:

I think that Dartman ment that the engine ran untill there was a malfunction in the charging system.

I have run my system on a race only car and also on a street driven car with no problems.

If you choose to switch the field wire the connection is made on whichever terminal on the kill switch that is used for the + cable connection. Also with this system the voltage regulator works just like factory. So the battery will charge.

I also noticed that someone said to run your -0 cable to the large terminal on the relay, which will work the same, the reason that I chose to run the cable to the starter instead was it took about two or three feet less cable. I used the cars existing + batt cable to run from the relay to the starter. Of course you have to cut the batt end off and swedge a loop type end on.

I also have a crimping tool that you use with a big hammer. I think that I bought it at Carquest. It works well.

Dennis J.

[chargerfreak]

Thanks Dennis. That was the answer I was hoping for And I'm glad you mentioned the main wire going to either the starter or the relay. I was wondering about that. Of course now I start working again tomorrow so this project will have to wait a week, but at least now I know exactly what I'm doing. I really appreciate all of the help.
Thanks again, Ben

[creative1]

i am pretty sure that on the mopars with two field wires, the voltage regulator controls the ground side of the field... any other reason for the isolated ground escapes me. this would mean that when the ignition switch is in the "on" position, the field immediately gets full battery voltage. and, since the regulator is controlling the ground, there will always be battery voltage to one side of the field, as long as the ignition switch is on. actually, i think that the power for the field actually comes from the unresisted side of the ballast resistor, which is also controlled by the ignition switch. the older single wire field (with the black, almost cubical regulator) controlled the field by a series of resistors that reduced the voltage going to the field. either way, if you find the field wire that has +voltage on it and run it through a disconnect switch AFTER it goes through the ignition switch (things get all interconnected there), you will effectively disconnect the field. i havent given this a lot of thought till now, but yes, you would probably have to have either a double pole switch, or wire a relay to do the switching for you. the relay could be fed from the main cable to the starter, as the master switch would disconnect this from the battery when it was turned to the "off" position. matter of fact, this would also eliminate a long run of wire, no matter what size it was. the relay should have a minimum current rating of 10 amps. hmmm... yeah... this would be the way to go... unless i missed something somewhere.

[Dennis Jokela]

Creative1:

I think that you are digging to deep and confusing yourself.

The key to the whole kill switch thing is that the field wire is connected to the + cable at the kill switch. Throw the switch, no battery power to the ignition switch, All power is disconnected.

You only have to switch one field wire on a dual field system.

Dennis J.

[creative1]

if the alt output and the alt field ever get connected, and they do at the ignition switch, and the alternator then becomes self-exciting, providing power for the rest of the electrical system untill the ignition switch is turned off. once the engine is running, the battery can be completely removed from the car and the engine will continue to run. there are only 2 ways to eliminate this that i know of, both of which reqire either 2 seperate switches (which would defeat the whole idea here, which is to kill the entire electrical system in the car) or some other way to isolate the alt field and the battery. hence either the dpst main disconnect switch at the rear of the car near the battery (which requires a long wire run from the alternator to this switch) OR a relay that controls either the field or the output. the choice is up to the individual. I would choose the field, because it carries much less current. this relay can also be mounted nearer the alternator, reducing the amount of wire necessary to do the job. this relay would be energized only when the main disconnect is in the "on" or "run" position. the drawback to the relay idea is that if the main disconnect switch is left in the "on" position, it will slowly run the battery down. the wire the relay controls (in my choice, the field wire) can still be switched by the ignition switch and the alternator field (and alternator) will function normally when the main disconnect switch is in the "on" position.

[Dennis Jokela]

Creative1:

If the kill switch is thrown (turned off) the ignition switch and everything on the other side of the battery is dead.

Ben:

After rereading my posts on this subject, I realize that I gave you some bad or confusing info which I will try and correct now.

The field wire is hooked to the side of the kill switch that the +cable from the battery is hooked to. Then a wire is hooked from the other side of the kill switch going to the starter.

Dennis J.

[23T]

[QUOTE]Originally posted by Dennis Jokela
[B]First off Chrysler does not use a remote solenoid. They have a starter relay either mounted on the firewall or inner fender panel.

I wired mine the easiest way that I could figure out. I used a -0 cable run from the big lug on the starter to one side of the cut off switch. The other side of the switch goes to the +terminal of the battery.

The - terminal of the battery is grounded in the trunk. I used the existing + battery cable as a wire from the big lug on the starter to the big lug on the starter relay.

I ran a 10 guage wire from a field wire to the rear of the car to the kill switch and back to the alternator. By switching the field wire of the alternator the engine will die when the kill switch is turned off.

I hope this is of some use to you.

Never Ever forget to flip that switch are you disconect is useless. The way we use a set-up like this is have all switches in the up or down position for race and be sure and go through the check list

[The Dartman]

I finished my master cutoff rewire tonight and it works great.

Since I couldn't understand HOW the field wire can be interupted when both sides of a cutoff switch are energized (one with battery volts, the other with alternator volts) I went ahead and used the tried and true method of using the alternator charging wire. This makes sense to me, in that I isolated the battery voltage, and the charging voltage on the same side of the disconnect. This ensures that there is no residual 12 volts power to the "car side" of the switch. I felt that the field wire example from above would only work IF the master cutoff would've had two circuits. It is myunderstanding that the field wires are charge to allow a spinning alternator to create electrical 12 volt current. But connecting the field wire to the always hot battery, as in the example above, the alternator will ALWAYS be in a charging state. The examples given did not give me any additional clues as to why this might work, even though I can't even say that it won't. I will also stress that a field wire when interupted WILL keep an alternator from charging. This is fact, yet the examples above never cut the power form the field wire. Heck, I can't even see how a relay would do the job either...

I did some extensive searching on the 'net on this subject and only found a small number of sites that even addressed a charging alternator and a cutoff switch. Most of them were Phord sites and they all interupted the charging alternator wire as in my example.

I have about $8.00 in 25 foot of 10 gauge wire, shrink tubing, and ring connectors. The job took me about 25 minutes, with 15 of those minutes spent removing my "mini tub" modified back seat and working around the cage it get it up and out of the way.

Dartman

[dirty dan]

Hey dart man
Sounds to me like you have got the job done.
However wouldnt it have been easier to install a switch
in the voltage regulator circut?
This way you would acomplish the same task and have a lot less
amps to deal with.
It seems to me to use the chargeing wire,you would need a very high amp switch or as mentioned a relay.