Pertronix - ballast wire needed w/ Flamethrower coil? tach wiring? HELP!?!

Discussion in 'Classic Mustang Specific Tech' started by oz, May 26, 2004.

  1. I am installing a Pertronix Ignitor and Pertronix Flame Thrower coil on my 1969 Mustang as part of a full engine rebuild. The issue of ‘ballast resistor’ has me confused. Where is the resistor on the ’69 Mustang? Is it just a wire or is there a ‘box’ or something that I can identify as a ballast? I read some of the other threads on this and am not completely clear.

    On the back of the instruction sheet it says that the Flame Thrower coil provides ‘resistance internally’ - 1.5 ohm….. Does this mean that I can wire the Pertronix Ignitor directly to the Pertronix coil? If I do this, do I just hook up the original wires from the harness the same as before?

    Tach – I have an aftermarket tachometer that wires to the ‘-‘ side of the coil. Is the Pertronix going to screw this up? If so, how do I get around it?

    I am trying to follow the wiring diagram in the '69 Mustang Service Manual but have had little luck….
    The circuit diagram shows the wire from terminal ‘I’ on the relay going to the coil. The wire I have on the ‘I’ terminal goes into the main harness that runs down in front of the radiator, along the left fender and through the dash and into the fuse block. I assume it comes back(?) There is a three wire connector on the engine side of the fire wall with one wire that that goes to the coil (the other wire in the points setup came from the distributor). There is also the ‘S’ terminal wire that goes through the switch and returns to the coil through a ‘resistance wire’ I have been unable to find it. The Pertronix shows the ‘+’ wire being spliced in to this wire after the key but before the coil – or in parallel….

    While were talking wiring - I also have two strange single wire connectors (both female - round in shape) on the firewall and another on the main harness that ends at the relay. What the heck is this? There is nothing attached to either of these wires… are they for diagnostic purposes? Sorry, I don’t trust the wiring on this car because during the teardown and rebuild I found that the voltage regulator was wired wrong. I wonder if somebody just started moving wires until the car ran…..

    I don’t want to mess this thing up and I tried to get contact info for Pertronix Technical Assistance without any real luck (general phone only). I can do all the mechanical things on this car but the electrical drives me nuts!

    Sorry this is so long…. I am just soooo confused. I can trace wires, etc if I absolutely have to but if somebody can tell me the right way I would love to avoid it....
    Any assistance would be greatly appreciated!!! THANKS
  2. the ballast is sometimes the wire, ford used stock wiring that had the ballast part contained in the wire that would knock the 12v down to 9v by the time the current got to the coil. Other times, its a metal block spliced in the middle of the wire somewhere and attached to an inside fender wall or there abouts, could be firewall, could be under the dash. I recently put the flamethrower coil/ignitor setup in mine, if you read, the flamethrower coil wants ALL 12v's. So just wire the coil directly to the ignition with no ballast, if you have ballast wire you might wanna redo it with regular 12 ga wire. As far as the tach, remember, electricity doesnt just JUMP out there, it has to be pulled by a source, so hooking up your tach on the '-' lead shouldnt be a problem for the tach.

    Hope that helps
  3. Thanks for the reply.... so the balast in the '+' side needs to be removed for the Pertronix coil to work properly?

    You're probably not going to believe that i am an engineer... Mechanical. I can wire my house but these 'primary' and 'secondary' loops are beyond my very basic electrical knowledge.

    Thanks again.
  4. In my 68, the pink wire running from my ignition switch to firewall is the ballast resistance, so I just bypass it with a new wire.
  5. Can you check the voltage at the coil to determine this? If the voltage checks 9, there's a resistor? Would you check it with the key on, engine off?
  6. The primary reason for the ballast wire these days is to prevent burning up points. You can run a full 12v to a non points ignition, modern day coils and distributors can take about anything youre going to throw at them.
  7. ok, i cant remember which is + and which is - but I know ur ignition lead from ur firewall goes to the (if ur looking straight on the coil from right infront of the car) to the RIGHT connection on the coil, then just connect the ignitor, its easy if you use the ignitor wiring diagram provided. But u are right, the petronix needs 12v to operate.
  8. yup you got the idea
  9. if im not mistaken* you check it with the car running
  10. Thanks for the replies. I (reluctantly) took the dash apart again (had to install a new speedo cable during the rebuild/upgrade project for my 3 speed to 4 speed conversion...) and found that the pink 'do not cut' wire goes from the connector just outside the fire wall to the ignition switch. I would love to get the pin out of the connector and solder the new 'bypass' wire to it but haven't had any luck yet. So, I plan to splice a new wire to the 'other' wire that goes to the same terminal on the switch (green with red I think - smaller gage) and then run the wire all the way to the coil. I will then use this wire instead of the one in the harness, thus bypassing the resistor wire without cutting it. That way if I want to go back to the stock coil later, I can without tearing the dash apart again.... Does this make sense?

    Thanks!!!!! :)
  11. yeah it makes sense, sounds good
  12. Your very confused friend.

    That is/was not the purpose of the ballast wire. The reason is that the coil was designed to operate at 9V. During starting the ballast wire is bypassed and the full 12V would go to the coil to make a hotter spark during starting.

    Nowadays coils are designed better and provide ample spark even during starting. So usually the ballast resistor is no longer needed.

    Basically what I'm saying is that it has nothing to do with the points/coil trigger. It's all in the design of the coil. To determine if you need a balast resistor, you must know how the coil was designed to run.