Hi there. We just installed a new MSD EFI on our 72 Challenger. All is hooked up and ready to go with the exception of one red wire that typically goes to the positive side of the coil on a regular car. But being this is a Dodge with a ballast resistor, it won’t work on the coil. Needs to be a 12v source with power for both key-on and cranking. Where or where would that source be? Any help? Please don’t say MSD or Tony Mopar. Neither were any help. Thanks much.

 

Should be a Dark Blue going to the ballast resistor. Check Mymopar wiring diagrams, there is a list of diagrams by year and model.

 

Thank you!

 

Back at my big computer.

http://www.mymopar.com/downloads/1972/72ChallengerA.JPG

 

Thank you again! You’ve been very helpful. Now just need to go check it out!