Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
Is it easy to get to a wire off the ign. switch on a column key car? Anyone know which wire to tap into to get power for both start and run? Or is going off of one side of the ballast better? (which side is the full power?)
Joined: Wed Jan 25 2006, 07:03PM
Location: Milford Mi
Posts: 403
Are you installing an MSD box? or something else? I would not pull power from the ignition system for anything else. Use a diode between the start and run wire it will let current flow in only one direction.
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
I need the power for the EFI ecu. Should be a very small draw, it's just the switched power to turn it on (like a relay) The actual power and ground sources go straight to the batt.
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
I must be asking this in a weird way because nobody is getting it
I need power that is on in both the start and run position. Not one or the other, but both in one circuit. The coil gets this kind of power through the ignition switch then on to the ballast resistor. I'm trying to ask the easiest/safest place to tap into that.
Does the ECU have a provision for driving the coil? If so, then you can eliminate the ballast and pick up power there. This is how I wired the PCM for my 94 Magnum EFI swap into my PowerWagon. The PCM controls and supplies the power to the coil, so the ballast is not needed. The same applies if using an MSD and Blaster coil, like I did on my Fury. In both cases the ballast was removed and the wires that originally came from the ignition switch and went to the ballast wire spliced together and then used to feed the PCM on the Magnum and the coil on the MSD. Each wire is only hot one at a time and transition smoothly as the key is released.
The other option would be to tie into those circuits and use them to control some relays. I would have to think a bit more about how to wire that though. A SPDT relay would work.
Joined: Thu May 01 2008, 11:15AM
Location: Chicago,IL
Posts: 2868
no need for a relay, as we're really talking about powering the signal side of a relay already. I still need the MSD to fire the coil. The ECU just takes input from the dizzy, alters it, and sends it to the points wire (white) of the MSD. I still have the ballast hooked up with that due to laziness.
So, splice the wires from the ballast together and add my signal wire to the mix and be done with it?
Joined: Fri Oct 07 2005, 12:03PM
Location: Central Ky.
Posts: 1575
That's about the only way to get Start/Run both on the same line. They just hit the 2 ends of the Ballast. If you get em' there you could always put it back to original easy if you wanted.
Technically only the Start voltage HAS to be gotten there, the Run could be anywhere there's Ign 12V under the hood.