switched power live while cranking

[Crash520]

Guys,
I know this has been asked before, maybe on other sites, but I need an under dash switched power that is also live while cranking to connect my EFI and CDI to, I think most use the old ballast wire connection to provide this but thats on the engine bay side, Im chasing the location of such under dash please. any help??

[dodj]

The same brown and blue wires are  on the cabin side of the firewall as well.  They come off the ign sw. Look at your column connectors. On the ign sw connector you will see the brown and blue wires you are looking for.

[Crash520]

Thanks mate

[Crash520]

Dish, am I simply tapping into both the dark blue and the brown and twist together??

[dodj]

Yup. The ballast resistor is where the brown and blue wires go. Most times people tie them together there. You are just going to do it before the bulkhead connector rather than after.

[Crash520]

Is there such a thing as an ignition switch wiring diagram out there???

Ok so they get twisted togeather and with the msd switched active wire and call it done

[HP_Cuda]

Why not use a relay by using the blue/brown wire as signal.

This way you are set and get a fresh 12v to your EFI.

[Crash520]

Happy to BUT is the blue wire constantly live when switching from run to start?, I thought that's why the brown and blue had to be connected together to maintain a constant on when switching from run to start, if it's not the relay is just going to open as the switch does, you need a patching relay on a timer etc otherwise

[Burdar]

The brown wire only has power in the "start" position.  The blue wire only has power in the "run" position.  During "start", the brown wire bypasses the ballast and supplies a full 12v to the coil.

If you connect the brown and blue wires together, the brown wire will have power in the "run" position.  You will be bypassing the ballast and be sending 12v to the coil.  This is fine if the coil you are using is designed to run off of 12v.  If not, you'll burn up the coil very quickly.

Four prong ballast   https://www.allpar.com/fix/miscpix/ignition/1.gif

Two prong ballast    http://www.allpar.com/fix/miscpix/ignition/2.gif

[Crash520]

Thanks Burdar, I'm not using a ballast resistor or std coil, it's being changed over to FAST XFI and CDI , but I need a source of constant switched power for both the EFI and CDI hence joining the two

[HP_Cuda]

This might help answer your questions:
https://forum.e-bodies.org/engine-transmission-and-rear-end/4/efi-fitech/1959/msg48253#msg48253

Looks like most tie both together for a signal or draw on one side of the ballast which gets key on and start voltage.

[dodj]

Ok so they get twisted togeather and with the msd switched active wire and call it done

Yes