removing ballast resistor WIRING, MSD, switched 12v source,

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rmchrgr

rmchrgr

Skate And Destroy
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OK, I'm installing an MSD 6AL in to the Duster. I'm not asking how to do that since its pretty self explanatory. However, I am going to try and do something slightly different, hence my questions. Sorry no pretty pics here, kind of going on what I have in my head.

In an effort to clean up/streamline the engine harness, I'm trying to remove any unnecessary wiring. (I'm totally dedicated to removing any unused/unnecessary stuff on my car) I actually took the entire engine harness out and unwrapped it so now I have everything separated and disconnected. Kind of easy to work on compared to some of the harnesses I'm used to dealing with from working at a dealer. And though it was working 'OK', the wiring in my car was somewhat convoluted and not very well executed - it was bothering me so I went ahead and started to try and clean it up.

So play along with me here, I know this may be a little unconventional but hopefully makes some sort of sense. Since I'm using the MSD which does not require a ballast resistor, I want to completely eliminate the ballast resistor wiring from the harness. I realize there are both the IGN 1 and 2 circuits (crank/run, one is hot only when cranking, the other hot only in run) in that leg of the harness. As I understand it, the blue is the run circuit and is spliced into the blue alt. field wire to the voltage regulator and the brown wire is the crank/coil +.

AFAIK, the MSD will control the coil internally. I'm thinking if I got rid of the brown wire, (remove it from bulkhead connector) the coil will work since now the MSD is telling it to fire. So then what about removing the spliced blue wire from the blue alt. to voltage reg. wire? I would essentially be removing the factory start/run circuit to let the MSD do it. I may be answering my own question here but again, please play along and see if what I am thinking holds any merit.

Next, I had the idea to run the red MSD signal wire directly to the fuse box instead of jumping the three B.R. wires together and splicing them to the red MSD signal wire which is how I interpret the MSD instructions. (in an MSD controlled system, coil gets 12V) I will mention that I no longer have a radio or heater so my accessories are limited to you guessed it, only the essentials - lights and wipers which never really get used anyway. Both the heater and radio should be switched 12V, right? I could connect the red signal wire right onto one of the unused fuse box blade terminals and have that circuit be fuse protected as well without splicing anything. Sound OK?

So again, I guess I'm essentially asking the MSD to control the start/run circuit - is this even possible? I have not read of anyone else doing it this way and I've been researching this for a little bit. I feel like I'm missing something but I'm not sure. My one thought is that the B.R. circuitry is needed to tell the ignition to turn on and stay on. Hard to understand why its spliced into the voltage regulator wire though. I'd really like to separate the two and make the charging circuit a stand alone harness. Oh yeah, I also am going to bypass the ammeter a la Mad Electrical - alt. output to starter relay, solder ammeter wires together yada yada.

Hope someone understands what I'm trying to do here or tell me I am completely over thinking/confused/dumb. Thanks for any input!

- Greg
 
I think you are overthinking it.
With my HEI ignitions removing the start and run wires back to the original harness works well and then the two connected together to run the Ignition system.
One or the other always has power to it whenever the key in on, and they don't interfere with each other as far as being connected together.

You are right in that any switched power source would work to supply your ignition also, just want to make sure you have a good strong supply and not some 15 foot long accesory wire that ends up with low voltage under a load.

You might even consider using a relay to get a good strong source, and just use the ignition on source to trigger the relay.
This would definitly go against your clean as possible goals though.

You might want to really consider using the start/run circuit that already exists, and just connect them together like I mentioned above.
 
I know I can twist the wires together and MSD essentially tells you to do it like that, just looking for a more *ahem* elegant solution.

May not be one.
 
You need the brown jumpered to the blue. I guess you could pull it out of the bulkhead and strap it to the blue "under the dash" which would clean up one whole wire. The reason you still need the brown is that on most older Mopars, the blue goes cold in "crank." Brown is the only "hot" wire supplying ignition power, so you still need something to trigger the MSD to "operate." "Trigger" in this case means triggering the power - up circuitry in the MSD, has nothing to do with triggering spark.

But you STILL need the blue "under the hood," depending on the year of your car and what's under there.

On the 70/ later cars the blue supplies power to

ignition (in this case MSD red trigger)

regulator power

alternator blue field wire

electric choke if used

Some smog doo dads on some cars, idle solenoid, etc. I don't remember where the A/C clutch comes from if used.

So in the end, there is not a heck of a lot that you can do away with.

You COULD clean up the blue where it splices off to things and hide that, along with a simple bullet, etc, connector for the MSD "small red"

Really, that's about it. After all, Ma didn't just throw a bunch of wire in there for the hell of it.
 
67Dart273 said:
You need the brown jumpered to the blue. I guess you could pull it out of the bulkhead and strap it to the blue "under the dash" which would clean up one whole wire. The reason you still need the brown is that on most older Mopars, the blue goes cold in "crank." Brown is the only "hot" wire supplying ignition power, so you still need something to trigger the MSD to "operate." "Trigger" in this case means triggering the power - up circuitry in the MSD, has nothing to do with triggering spark.
Click to expand...

The MSD gets power directly from battery +. It's electronic, no?

67Dart273 said:
But you STILL need the blue "under the hood," depending on the year of your car and what's under there.

On the 70/ later cars the blue supplies power to ignition (in this case MSD red trigger); regulator power; alternator blue field wire; electric choke if used; Some smog doo dads on some cars, idle solenoid, etc. I don't remember where the A/C clutch comes from if used.

So in the end, there is not a heck of a lot that you can do away with.

You COULD clean up the blue where it splices off to things and hide that, along with a simple bullet, etc, connector for the MSD "small red"

Really, that's about it. After all, Ma didn't just throw a bunch of wire in there for the hell of it.
Click to expand...

Trying to ascertain whether or not I can separate the blue IGN wire from the blue alternator wire without any ill effects. I'm thinking the alt. wire is how the IGN run wire is powered though, being spliced into and all. Could the MSD signal wire provide the same low current for the run circuit as the blue alt field wire?
 
I think in a way you are asking if the power wire for the MSD can also be your alt feild wire.
Is that right?
 
TrailBeast said:
I think in a way you are asking if the power wire for the MSD can also be your alt feild wire.
Is that right?
Click to expand...

No, not at all. The ign run wire for the OE system is spliced into the alt. field wire. As I understand it, the blue alt field wire powers the run circuit. I would like to separate those circuits to make it easier to connect the MSD signal.

If I can't get rid of something, its fine but I would like to see if I can come up with a better idea than just tying all these wires together with a giant crimp or what have you.
 
rmchrgr said:
No, not at all. The ign run wire for the OE system is spliced into the alt. field wire. As I understand it, the blue alt field wire powers the run circuit. I would like to separate those circuits to make it easier to connect the MSD signal.

If I can't get rid of something, its fine but I would like to see if I can come up with a better idea than just tying all these wires together with a giant crimp or what have you.
Click to expand...

You have this all backwards.

The ignition dark blue run with key in "run" is a SOURCE of power

The brown "in start" is a SOURCE of power

All of the "stuff" that the ignition blue "run" "goes to" under the hood MUST have power to operate, and it comes FROM the source, IE the ignition switch.

The MSD "small red" is either a solid state or a relay, and is a "control" line, like a relay. The great big red power wire for the MSD does nothing for the box until the "small red" RECEIVES switched 12V to activate the box.

Likewise, the regulator and alternator field RECEIVE power from the dark blue coming from the ign switch.

Also important, as you've no doubt "read" me preach on here, is the harness voltage drop, because the regulator IGN terminal is also the "battery sense" terminal. That is the terminal from which the regulator.......regulates.

If that line, coming from the ignition switch is low, the charging voltage RAISES by whatever amount of drop there is. This is because the regulator "thinks" that battery voltage is that much low.
 
Would there be any issue with tying the IGN 1 + 2 together coming out of the ignition switch under the dash and before it passes through the bulkhead? Maybe I could use a junction block sort of thing with ring terminals?

Again, I'm not trying to eliminate the start/run circuit, just the ballast resistor wiring beyond the bulkhead connector since it won't be used.
 
rmchrgr said:
Would there be any issue with tying the IGN 1 + 2 together coming out of the ignition switch under the dash and before it passes through the bulkhead? Maybe I could use a junction block sort of thing with ring terminals?

Again, I'm not trying to eliminate the start/run circuit, just the ballast resistor wiring beyond the bulkhead connector since it won't be used.
Click to expand...

yes..you can do that....Did it on a 71 Dart...
 
Cool, thanks Tony.

Hate to beat a dead horse but how did you do it? Did you use a block? Crimp? Want to make it reliable.
 
rmchrgr said:
Cool, thanks Tony.

Hate to beat a dead horse but how did you do it? Did you use a block? Crimp? Want to make it reliable.
Click to expand...

So all this gets down to what I told you in the first place---you can eliminate one whole wire
 
67Dart273 said:
So all this gets down to what I told you in the first place---you can eliminate one whole wire
Click to expand...

Well, that's OK. I realize its probably more work than its worth. Again, I like things to be sanitary, what can I tell you.

I'm also in favor of minimizing points of potential failures. Why leave a wire hanging loose if you can cut it out?

True, leaving the one little wire there would not have amounted to much but nothing ventured, nothing gained.
 
I soldered and heat shrinked mine when I tied them together.
Solid and reliable.

Mine are tied together under the hood right at the harness, then I powered the coil off of them.
Tying them together behind the dash is simple also.
 
I had a spare ignition switch...using a ohm meter...I was able to tell which two wires I needed to tie together to get the start/run circuit together.....

dont ask..I dont remember...LOL
 
70aarcuda said:
I had a spare ignition switch...using a ohm meter...I was able to tell which two wires I needed to tie together to get the start/run circuit together.....

dont ask..I dont remember...LOL
Click to expand...

I had a key and a test light. :D

I know I'm a smartass.
 
Wouldnt using the two wires connected to actuate a relay that can handle the current the best thing to do? All that could be hidden from view, then one good adequate guage wire going to one side of the relay to the + on the battery and the other side going to the MSD? Either put the relay next to the MSD, or if the battery is in the trunk, have the relay next to the battery, then you got one single wire running in the engine compartment to the MSD. BTW, trunk mounted batterys make engine bays look SO MUCH cleaner!

EDIT: If this is done, but an adequate fuse in the wire from battery to relay as close to the battery as possible.
 
Dragonbat13 said:
Wouldnt using the two wires connected to actuate a relay that can handle the current the best thing to do? All that could be hidden from view, then one good adequate guage wire going to one side of the relay to the + on the battery and the other side going to the MSD? Either put the relay next to the MSD, or if the battery is in the trunk, have the relay next to the battery, then you got one single wire running in the engine compartment to the MSD. BTW, trunk mounted batterys make engine bays look SO MUCH cleaner!

EDIT: If this is done, but an adequate fuse in the wire from battery to relay as close to the battery as possible.
Click to expand...

Sure, that would be the absolute best way, but the relay would kind be pain to hide in a reasonable place.
If you could put the relay right next to the MSD would even be better, but then there's the extra stuff again.
 
Dragonbat13 said:
Wouldnt using the two wires connected to actuate a relay that can handle the current the best thing to do? All that could be hidden from view, then one good adequate guage wire going to one side of the relay to the + on the battery and the other side going to the MSD? Either put the relay next to the MSD, or if the battery is in the trunk, have the relay next to the battery, then you got one single wire running in the engine compartment to the MSD. BTW, trunk mounted batterys make engine bays look SO MUCH cleaner!

EDIT: If this is done, but an adequate fuse in the wire from battery to relay as close to the battery as possible.
Click to expand...


Yep, battery is in the trunk with a 4 pole cut off switch. I like the idea of a relay but wouldn't there be two control stages in one circuit? (crank then run) Not sure how to wire it with a relay.
 
OK when you twist those two wires together and use a relay, your going to only need one wire, from that pair, going to the relay. The relay will have two terminals that actuate the relay (control terminals), and two that will allow voltage to flow through when the relay is actuated. Right at the twisted wires, or as close to the switch as possible, put a fuse holder in that line to protect the wiring from the switch to one of the control terminals. Run the other control terminal to ground on the car. Right next to the relay, or too the negetive of the battery. OK the control circuit is done. Make sure you know which terminals are controll terminals.

Then use ADEQUATE wire from the battery positive to an Adequate fuse holder and fuse, as close to the battery as possible. From the other side of that fuse go to the MSD. This wire should be heavier gauge than the relays controll wiring. It needs to be able to supply enough current to support the length of the wiring and the MSD.

This setup will protect everything, keep from burning down the car, put one wire in the engine bay for the ignition positive, and prevent the voltage drop 67 dart is talking about. That voltage drop is important to consider, you dont want your alternator putting out more than necessary.
 
Dragonbat13 said:
OK when you twist those two wires together and use a relay, your going to only need one wire, from that pair, going to the relay. The relay will have two terminals that actuate the relay (control terminals), and two that will allow voltage to flow through when the relay is actuated. Right at the twisted wires, or as close to the switch as possible, put a fuse holder in that line to protect the wiring from the switch to one of the control terminals. Run the other control terminal to ground on the car. Right next to the relay, or too the negetive of the battery. OK the control circuit is done. Make sure you know which terminals are controll terminals.

Then use ADEQUATE wire from the battery positive to an Adequate fuse holder and fuse, as close to the battery as possible. From the other side of that fuse go to the MSD. This wire should be heavier gauge than the relays controll wiring. It needs to be able to supply enough current to support the length of the wiring and the MSD.

This setup will protect everything, keep from burning down the car, put one wire in the engine bay for the ignition positive, and prevent the voltage drop 67 dart is talking about. That voltage drop is important to consider, you dont want your alternator putting out more than necessary.
Click to expand...

:thumrigh: I'll look into this method, sounds reasonable.
 
rmchrgr said:
Well, that's OK. I realize its probably more work than its worth. Again, I like things to be sanitary, what can I tell you.

I'm also in favor of minimizing points of potential failures. Why leave a wire hanging loose if you can cut it out?

True, leaving the one little wire there would not have amounted to much but nothing ventured, nothing gained.
Click to expand...

Look up "young gun" or whatever his name is, sorry. has the lime project. Ran the wiring under the fenders, moved all the components up under the dash. Really cleaned up the bay

You don't really need a relay FOR the MSD as that's the whole purpose of the small red wire -- to activate the box. I don't know if MSD uses a solid state switching device internally or they actually may USE a relay, so you'd be using a relay to feed a relay.

What you need a relay FOR is in reality to supply the regulator, IE to get the regulator power supply as close to battery voltage as possible.
 
OK, more thinking. (look out!)

Take the blue and brown wires out of the back of the B.H. connector on the dash side.

Take 5 pin ISO relay;


  • Brown wire to 87 (crank)
  • Blue wire to 87A (run)
  • Red MSD signal wire to 86 (powered by 87 then 87A for each switch state)
  • Battery + to 30
  • Ground wire to 85
So, the ignition switch energizes the brown wire pulling the coil in and energizing the red wire at start. Then when the key is released to run, the blue wire is energized and the red wire still remains energized.


This would be behind the dash so these wires would no longer be going through the bulkhead and I could eliminate the B.R. wires from the harness.


Sound good?





​
 
TrailBeast said:
There ya go.
Click to expand...

Cool, thanks. Thought that might be OK. No splicing, twisting etc and the individual start circuits are separated by the relay.

Only potential issue I could come up with is when the key is released from the start position to run on the switch, there is moment when there is no power. I doubt it would cause any trouble though.
 
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