Electrical Help

[71Demonz]

Hi,
Can someone please school me.  I need a 12 volt power source that is available in both the "On/Run" and "Crank" positions.  It must be prior to the ballast resistor.  Everything I have checked is either one or the other, not both.
Your help is greatly appreciated.
Thanks
Steve, 71 Barracuda

[mopardave]

Under the dash at the bulk head you have 2 openings on the bottom of the fuse block , one  is battery one is accessory.

[Bullitt-]

Not positive about this but I think the instruments get power with both ON & start/crank, I know most switched circuits are interrupted....

[GoodysGotaCuda]

I don't think anything besides the ballast is hot in both key positions. Gauges shut off, radio shuts off, etc when in 'start'. Starter relay is only hot in crank and not run.  Only thing it needs to be doing during cranking is firing.

What are you trying to do or diagnose?

[Chryco Psycho]

there is a brown wire & blue wire at the Ballast you need a pigtail to tie the 2 into a circuit to fire MSD or other ignitions

[71Demonz]

Hey guys.
Thanks for your replys.  I am installing a Professional Products Powerjection 3 fuel injection system on my big block.  The "key" position to the ECM requires power in the ON and Crank position. 
Chryco, thank you for posting, I think that is the only way I will be able to get what I need.  Are there any concerns I need to worry about in pigtailing those two wires together? 

[dodj]

Are there any concerns I need to worry about in pigtailing those two wires together?

None that I can think of. Many of us have them tied together ( as CP said) for MSD ignitions.

[71Demonz]

So does this mean I can eliminate my ballast resistor?  I am still using the Mopar Performance Electronic Ignition kit with the orange box ECU. 
Again, thanks for all the info. 

[mopar12372]

no

[hooD]

there is a brown wire & blue wire at the Ballast you need a pigtail to tie the 2 into a circuit to fire MSD or other ignitions

thought a picture would help out, of course this one has not been modified

[UKcuda]

I think you'll have to use a relay.

If you connect the blue and brown wires you will have the ballast resistor bypassed all the time whereas you need it in circuit for your Mopar ignition.

[dodj]

Just thinking a bit about using a relay...You might have to use two in order to keep the blue and brown separate. If you put the brown and blue under the same (relay coil) screw you are effectively doing the bypass bit. If you used two relays and tied their output together to supply the FI unit, the ballast cct would be intact. 

Hmmm...seems like there should be a simpler way.

[UKcuda]

Just thinking a bit about using a relay...You might have to use two in order to keep the blue and brown separate. If you put the brown and blue under the same (relay coil) screw you are effectively doing the bypass bit. If you used two relays and tied their output together to supply the FI unit, the ballast cct would be intact. 

Hmmm...seems like there should be a simpler way.

You can do it with one relay if it's a double pole relay.

I can't remember which is blue and which is brown so I'll say "cranking" and "run" feeds instead.

Wire the cranking feed so it goes through the relay contacts when the relay is not energised and wire the run feed so it energises the relay.  Also wire the run feed (or any 12v source) to go through the relay contacts when the relay it is energised.

[71Demonz]

You can do it with one relay if it's a double pole relay.

I can't remember which is blue and which is brown so I'll say "cranking" and "run" feeds instead.

Wire the cranking feed so it goes through the relay contacts when the relay is not energised and wire the run feed so it energises the relay.  Also wire the run feed (or any 12v source) to go through the relay contacts when the relay it is energised.

Thanks UKcuda.  That sounds like an excellent option.  By the way I found the very informative and detailed explanation you wrote on the purpose of ballast resistor.  It was a wonderful read. Thank you

[dodj]

You can do it with one relay if it's a double pole relay.

I can't remember which is blue and which is brown so I'll say "cranking" and "run" feeds instead.

Wire the cranking feed so it goes through the relay contacts when the relay is not energised and wire the run feed so it energises the relay.  Also wire the run feed (or any 12v source) to go through the relay contacts when the relay it is energised.

That's simpler UK!