12 volt source in run and start

[Chickenman21]

Hooking up FAST FI system and need 12 v in run and start mode. Which wire under the hood will give me 12v in start and run?

I have upgraded alternator and Mopar electronic ignition (orange box). I have purchased the M&H harness for upgraded alt and electronic ignition. I have switched the voltage regulator to match the M&H harness and switched to 4 post ballast to match the harness.

Thanks for your help.

 

[oldbee]

Should be dark blue or brn going to ballast resistor per ‘68 FSM. Only you could’ve got me away from watching MASH on tv.lol. 1stMarDiv 70-71. Semper Fi you old guy!

 

[Yatzee]

Some would say that the same wire that connects to the coil from the ballast but I strongly disagree. There is too much "noise" connecting to any ignition supply wire and it can adversley affect the operation of the ECU of the TB unit. You are best to install (in an inconspicuous spot) a separate relay and power the unit with that. Power the relay with the existing ignition power wire but run a separate fused source wire for power to the TB.

 

[Chickenman21]

Should be dark blue or brn going to ballast resistor per ‘68 FSM. Only you could’ve got me away from watching MASH on tv.lol. 1stMarDiv 70-71. Semper Fi you old guy!

Like you haven't seen every episode a dozen times. LOL. My brother was a Marine in RVN 69 - 70. Semper Fi right back at you from me and my brother.

I have the 1969 service manual but the wiring schematic shows the 2 post ballast resistor with the blue and brown wires. The new harness and four post ballast resistor has like 5 wires and I'm not sure which post / wire will give me a steady 12v. Thanks for the help.

 

[Nacho-RT74]

there is NO WAY to get full 12 volts on stock harness for anything on both ign stages

If keeping stock ign system with ballast in line this could be the only way to get full 12 volts on both ign switch stages without affect the ballast function to the coil

I made diagram showing dual ballast... single ballast the same just despiting the secondary resistor section to the ECU ( green traced red wire )

 

[5.7 hemi]

Why not jumper ign.1 and ign.2 together at the switch?

 

[451Mopar]

there is NO WAY to get full 12 volts on stock harness for anything on both ign stages

If keeping stock ign system with ballast in line this could be the only way to get full 12 volts on both ign switch stages without affect the ballast function to the coil

I made diagram showing dual ballast... single ballast the same just despiting the secondary resistor section to the ECU ( green traced red wire )

View attachment 594485

The diode method above works, but I don't recall the diode part number. I think it is a 10 amp diode?
This method retains the ballast resistor for the coil and stock ECU.
If you are using a coil that has internal ballast resistor, or ignition system like a MSD that drives the coil itself, then you can connect the run and start wires together (coil ballast resistor not used.)

 

[Nacho-RT74]

Why not jumper ign.1 and ign.2 together at the switch?

because is the same than bypass the ballast. will be feeding the wire what bypass the ballast coming from run circuit.

 

[Nacho-RT74]

The diode method above works, but I don't recall the diode part number. I think it is a 10 amp diode?
This method retains the ballast resistor for the coil and stock ECU.
If you are using a coil that has internal ballast resistor, or ignition system like a MSD that drives the coil itself, then you can connect the run and start wires together (coil ballast resistor not used.)

can't talk about the propper diode. I actually know nothing about diodes LOL, just how they work, but not the propper one to be used

and of course, I'm talking just from the stock ignition system point of view... any other will be diff

 

[5.7 hemi]

Could you hog out the ballast resistor and take that wire out, solder a new wire in between and/also tie ign.1/2 together at the key?

Or is that doing the same thing?

 

[Nacho-RT74]

everything that links out both circuits aside of the stock resistor will feed constant 12 volts to the coil on RUN, and thats not healthy for the coil. That's the reason for the diode if needing 12 volts while cranking but keep the lower voltage while running to the coil.

remember the ign switch never feeds both circuits at the same time, but the ballast joins them. At diff stages both circuits are hot but at diff voltage levels depending on which side of the resistor is being feeded from ign switch. Thats why even the ign switch is not feeding from RUN ( ign1 ) while cranking, you still get voltage there, but coming from START ( ign2 ) through the ballast on lower voltage rate. And thats why the brake ( and oil ) light on cluster dimms while cranking

 

[Nacho-RT74]

That decay on voltage at RUN circuit is what made to install on later 70s models an extra relay circuit to feed the regulator, Keeping it working at the correct voltage rate while you are cranking the same than when in RUN

 

[5.7 hemi]

Since the OP is going efi, he needs 12 volts at run and crank. So a different coil should be used anyway. So having ign1/2 tied together at the switch is what is needed. I had to do this for my dads 70’ Challenger RT when he went to efi.

 

[Chickenman21]

Since the OP is going efi, he needs 12 volts at run and crank. So a different coil should be used anyway. So having ign1/2 tied together at the switch is what is needed. I had to do this for my dads 70’ Challenger RT when he went to efi.

Thanks, 5.7. I believe your method will be best.

 

[5.7 hemi]

No problem

 

[Nacho-RT74]

OK, if the coil will be sourced diff than the stock system, that’s another deal, I’m just talking from the stock ignition system point of view.

 

[451Mopar]

Which FAST system EZ-EFI or XFI? Just curious, I have the XFI 2.0 for the Coronet.

 

[5.7 hemi]

The EZ sucks! It does work, and my dads has been on now for 3-4 years and every now and again there’s some pinging he can hear. Also could be the crappy Ca. gas we have.

 

[Chickenman21]

Which FAST system EZ-EFI or XFI? Just curious, I have the XFI 2.0 for the Coronet.

EZ-EFI. Have been running it for a couple of years with no problem until my factory wiring burned up on me. The wiring issues had nothing to do with the EFI and I do not think the EFI wiring was affected but will not know until I finish the wiring repairs.

 

[Chickenman21]

The EZ sucks! It does work, and my dads has been on now for 3-4 years and every now and again there’s some pinging he can hear. Also could be the crappy Ca. gas we have.

Been running my EZ EFI for a couple of years without any issues with the system. I just do not like all the wiring harnesses it has. Looks like a snake pit under the hood. Luckily my large Air Grabber breather helps hid them.