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#955206 - 03/21/11 10:26 AM MSD 6AL key on voltage connection
gtx6970 Offline
I Live Here

Registered: 06/28/03
Posts: 17065
Loc: Land of Booze and Horses
What is the prefered circuit for the key on signal B+ connection for the MSD box

It's a new M+H Wiring stock underhood wiring harness in a 1970 Road Runner

MSD box is going to be under the battery tray and I plan to use the radiator support for the primary ground and the B+ post on the starter relay for battery positive. And will be routed along the factory fenderwell and firewall wiring but not wrapped into it.

My initial thoughts are the J3 circut off the ignition switch coming thru the firewall bulkhead connector - using the original feed wire for the stock coil ( stock ballast will be there but non-functional)


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#955207 - 03/21/11 12:40 PM Re: MSD 6AL key on voltage connection [Re: gtx6970]
87MO DAK Offline
member

Registered: 12/09/10
Posts: 114
Loc: NY,Poughkeepsie
MSD boxes should power and ground directly off the battery
,and no where else . The trigger wire (small red ) just needs
a 12 volt key on hot wire , to tell the box to switch on.

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#955208 - 03/21/11 01:27 PM Re: MSD 6AL key on voltage connection [Re: 87MO DAK]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 5004
Loc: Caracas, Venezuela, SouthAmeri...
actually with a good power coming from alt and healthy wiring, the B+ source it can be wired from alt post too

the KEY source it can be the blue wire ( brown in 70 and lates ) going from ballast to coil.

Or if thinking on remove ballast resistor, then use the blue wire ( all years ) originally feeding ballast and regulator

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#955209 - 03/21/11 01:31 PM Re: MSD 6AL key on voltage connection [Re: 87MO DAK]
gtx6970 Offline
I Live Here

Registered: 06/28/03
Posts: 17065
Loc: Land of Booze and Horses
Quote:

The trigger wire (small red ) just needs
a 12 volt key on hot wire , to tell the box to switch on.




Any suggestions as to what circuit to get the key on signal from ?

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#955210 - 03/21/11 01:32 PM Re: MSD 6AL key on voltage connection [Re: NachoRT74]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 5004
Loc: Caracas, Venezuela, SouthAmeri...
Quote:


the KEY source it can be the blue wire ( brown in 70 and lates ) going from ballast to coil.

Or if thinking on remove ballast resistor, then use the blue wire ( all years ) originally feeding ballast and regulator



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#955211 - 03/21/11 01:48 PM Re: MSD 6AL key on voltage connection [Re: NachoRT74]
87MO DAK Offline
member

Registered: 12/09/10
Posts: 114
Loc: NY,Poughkeepsie
Coming directly off the alt will put lots of noise in the MSD box ,
by going directly to the batt the alt noise will get filtered.

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#955212 - 03/21/11 11:10 PM Re: MSD 6AL key on voltage connection [Re: 87MO DAK]
MarkM Offline
Worthy

Registered: 01/13/05
Posts: 2185
Loc: USA, MI
Quote:

Coming directly off the alt will put lots of noise in the MSD box ,
by going directly to the batt the alt noise will get filtered.




The wiring directions explicitly say not to wire it to the alternator post for this reason.

You can get 12v+ switched from the positive side of the electric choke harness.
_________________________
'87 Fifth Avenue: 512 low deck roller / 518 / 8.75


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#955213 - 03/21/11 11:58 PM Re: MSD 6AL key on voltage connection [Re: MarkM]
70AARcuda Offline
master

Registered: 01/20/03
Posts: 9673
Loc: las vegas
just remember the msd start switch will need to see 12 volts both went the key goes to start and went the key is on run...

some 12 volt circuits go to zero volts went the key goes to start...

take the two wires from the ballast resistor...run and start ...and connect both wires to the msd start switch...
_________________________
Tony

70 AARCuda Vitamin C
71 Dart Swinger 360 10.318 @ 128.22(10-04-14 Bakersfield)
71 Demon 360 10.666 @122.41 (01-29-17 @ Las Vegas)
71 Duster 360 (10.641 @ 124.17 9/16/16 Bakersfield)

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#955214 - 03/22/11 08:57 AM Re: MSD 6AL key on voltage connection [Re: 70AARcuda]
gtx6970 Offline
I Live Here

Registered: 06/28/03
Posts: 17065
Loc: Land of Booze and Horses
Quote:


take the two wires from the ballast resistor...run and start ...and connect both wires to the msd start switch...




This is what I'm going to do . Plan is to remove the 2 male spade connectors from the bulk head connector and wire the MSD box into both pinouts on the connector.
That way should the desire to remove all the hotrod stuff arise and put it back to stock. I want it to be as simple and painless as possibile

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#955215 - 03/22/11 09:02 AM Re: MSD 6AL key on voltage connection [Re: gtx6970]
DirectSubjection Offline
Tacohead. The First and Only

Registered: 01/19/03
Posts: 68692
Loc: Middlesex County, New Jersey
I found a 12-volt keyed source under the dash and hooked my MSD to that.

Turns out I hooked it to the key buzzer - my car starts fine but doesn't shut off until I physically remove the key from the ignition slot.
_________________________

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#955216 - 03/22/11 09:32 AM Re: MSD 6AL key on voltage connection [Re: gtx6970]
87MO DAK Offline
member

Registered: 12/09/10
Posts: 114
Loc: NY,Poughkeepsie
Quote:

Quote:


take the two wires from the ballast resistor...run and start ...and connect both wires to the msd start switch...




This is what I'm going to do . Plan is to remove the 2 male spade connectors from the bulk head connector and wire the MSD box into both pinouts on the connector.
That way should the desire to remove all the hotrod stuff arise and put it back to stock. I want it to be as simple and painless as possibile




If the car is still wired the way it cam factory ,
(main feed off alt through the bulk head to the amp gauge
then back out of the bulk head to starter relay or batt?)
You will still be in line with the alt.

What MSD is saying for the box to work the way it should,
is that it needs to be hooked to the battery POS&NEG only
and no where else.The battery will filter out most of the noise in the system .
If you wire it up any other way you could have erratic idle problems,
Fouling plugs ,remember the MSD box feed's the coil all it's power.


Attachments
6543313-msd102.jpg (112 downloads)


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#955217 - 03/22/11 09:49 AM Re: MSD 6AL key on voltage connection [Re: 87MO DAK]
gtx6970 Offline
I Live Here

Registered: 06/28/03
Posts: 17065
Loc: Land of Booze and Horses
But if I use the original coil pos connection to supply key start/on voltage signal it's using the ballast resistor .

Running it thru the ballast resistor and I tend to think this is abad idea , correct ?
UNLESS I run a solid wire to bypass it on the backside of the ballast.

It is a MSD dist btw, combined with an MSD blaster 2 coil.

And yes, all the cars body wiring is still stock. One of my goals here is to be able to return it back to stock with minimul effort should the desire to arise sometime in the future.

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#955218 - 03/22/11 10:00 AM Re: MSD 6AL key on voltage connection [Re: gtx6970]
87MO DAK Offline
member

Registered: 12/09/10
Posts: 114
Loc: NY,Poughkeepsie
Quote:

But if I use the original coil pos connection to supply key start/on voltage signal it's using the ballast resistor .

Running it thru the ballast resistor and I tend to think this is abad idea , correct ?
UNLESS I run a solid wire to bypass it on the backside of the ballast.

It is a MSD dist btw, combined with an MSD blaster 2 coil.

And yes, all the cars body wiring is still stock. One of my goals here is to be able to return it back to stock with minimul effort should the desire to arise sometime in the future.

It should be easy then , hook the main POS & NEG from the MSD box
directly to the battery.
Hook the smaller red wire to the blue wire on the ballast but hook it
up on the same side as the feed ,so if you want to remove it ,it should be pretty simple ,and that way it is not feeding through the ballast.

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#955219 - 03/23/11 01:09 AM Re: MSD 6AL key on voltage connection [Re: NachoRT74]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 5004
Loc: Caracas, Venezuela, SouthAmeri...
Quote:

Quote:


the KEY source it can be the blue wire ( brown in 70 and lates ) going from ballast to coil.

Or if thinking on remove ballast resistor, then use the blue wire ( all years ) originally feeding ballast and regulator







when I made this quote it was because forgot to add ( twice ), if removing ballast, NEED to splice together brown and blue wires coming from bulkhead to hook there the small red wire of MSD. If not remove the ballast wire going originally to coil is simply enough. Its just a trigger to turn it on, not a power source

Noises on system are actually produced from COIL on stock system, breaker points &/or mechanical regulators, not really the alt, but whatever! Follow the instructions going to batt or starter relay stud. Just take in mind SOME of the ammeter reading can it be some mismatched with the real status

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#955220 - 03/23/11 01:12 AM Re: MSD 6AL key on voltage connection [Re: 87MO DAK]
NachoRT74 Offline
master

Registered: 08/14/07
Posts: 5004
Loc: Caracas, Venezuela, SouthAmeri...
Quote:


Hook the smaller red wire to the blue wire on the ballast but hook it
up on the same side as the feed ,so if you want to remove it ,it should be pretty simple ,and that way it is not feeding through the ballast.




Partially true... On start moment, it will be triggered through ballast anyway

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