# Looking for the Ballast Resistor on a 69 GTO



## Old Indian (Jul 4, 2007)

I have a 69 GTO with a Pertronix kit in the distributor but the voltage drops at RPM. I assume it is because of the ballast resistor or resistor wire between the run lead at the ignition switch and the coil. Can anyone tell me where the resistor wire is located? 68 and below had the ballast on the firewall. 69 changed when the ignition switch moved to the column, but I can't find the resistor wire in the shop manual.


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## geeteeohguy (Feb 2, 2008)

I've had 9 GTO's: all '65-'67's. NONE of them had a ballast resistor on the firewall. They all used a resistor wire to the negative side of the coil. Not sure of the resistance value, but charging system/batt voltage is dropped to around 9--10 volts. All the above listed cars were stock ignition, though. No pertronix. Hope this helps. 
Jeff


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## Old Indian (Jul 4, 2007)

Thanks, Jeff. I'll check that side. I was working the run circuit to the positive side and couldn't find anything resembling a resistor wire. The ones I've seen have a significant bump usually wrapped in tape or shrink tubing. I'm seeing the voltage at the positive terminal of the coil drop as RPMs rise. Five grand and it's down around 9-10 as you say. The pertronix unit calls for 12 vdc continuously. That's why I'm trying to eliminate the resistor.


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## Rukee (Feb 8, 2007)

You could run a new wire from the ignition switch to the coil.


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## 05GTO (Oct 6, 2004)

Rukee said:


> You could run a new wire from the ignition switch to the coil.


:agree

In 69 they went to a single wire to the + side of the coil, prior years used 2 wires to the coil, one from the "on" side (resistor wire) of the switch and the other from the starter solenoid "s" connection (12 volt).

I don't have schematics but I believe the resistor was placed prior to the ignition switch which means the "on" wire would not include an inline ballast resistor. You may be able to splice a wire from a non-fused switched 12 volt supply to the current wire leading to the coil from the switch.

Measure the resistance from the on position of the switch to the + terminal of the coil. If it is a direct short splice anywhere under the dash to keep the stock appearance under the hood.


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## geeteeohguy (Feb 2, 2008)

Hi Old Indian. I made a mistake in my earlier post: I meant the POSITIVE side of the coil (B+)! That's the side the resistor wire is on. And, strangely, they look like a regular wire...no bulges, etc. You could use an ohmmeter to check. The above suggestions are all good ones. Sounds like you need 12 volts plus to run your system. Good luck!

Jeff


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## Old Indian (Jul 4, 2007)

Thanks, Guys. I appreciate the good ideas. I found a schematic that shows two wires from the ignition switch (start and run) to a common point on the firewall connector. The resistor wire should be the one from the run terminal. That explains why nothing showed up in the engine compartment on either the + or - wires to the coil. The jumper sounds like a good idea. I can pick up switched 12v from the fuse panel next to the firewall connector. Thanks for the advice. I just replaced the turn signal switch and found that the connector was not the correct one. This was a Delco replacement part. The good thing was that the pins could be pushed out of the new one and pushed into the old connector. Mission accomplished.


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## Rukee (Feb 8, 2007)

I would wire your coil wire to the ignition switch, not the fuse panel.


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## rob69gto (May 14, 2018)

For anyone who lands here like I did, converting from points to not points (pertronix ignitor I, flamethrower coil in this case). Vehicle would kick over but not run after the conversion. Jumpering 12v from the battery directly to the coil + terminal confirmed the in-line resistance in the "Run" circuit (as the vehicle would then start and run normally).

Wire is black with pink lettering printed along the wire body "Resistance Wire - Do Not Cut". I had a chuckle since other research indicated it might be cloth covered or unusual in some way. Vehicle is a 1969 base model, automatic trans, base 400ci engine. The wire goes from a pin out on the ignition module on base/top of steering column through main wiring trunk up and around and down to the fuse panel/firewall passthrough plug. It shares a pin with the 12g yellow wire that also comes out of the ignition module on the column.

Per the wiring diagram the yellow wire goes hot via the ignition module when the key (on column) is turned to start. Full 12v is provided. When key detents back to the "Run" position, yellow wire goes cold and resistance wire provides reduced voltage.

My plan is common the 12g pink (which shares the resist wire pin out on the ignition module) with the 12g yellow. This will provide a 12v leg bypass along the yellow wire when the key is in the "Run" position.


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## BearGFR (Aug 25, 2008)

If you want the dead nuts easiest solution to running a non-stock ignition system that needs the full 12-volts to operate, then don't mess with trying to locate/remove/replace the resistor wire at all. Instead, get yourself a generic headlight relay from your local parts store. Mount the relay at a convenient spot near the ignition. (Mine's on the firewall) Disconnect the wire that used to go to the B+ terminal on the coil (the primary ignition wire that has the resistance in it) and instead connect it to the energizer circuit of said relay with the other terminal on that circuit going to a good ground. Wire the other side of the relay to a convenient full 12v source and connect the output of that from the relay to your ignition input. Problem solved. You now have full power to your ignition, and you didn't have to hack up your wiring harness to get it. If you ever decide to go back to 100% factory stock -- it's simple.

Bear


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## Dave Ray (May 18, 2018)

The ballast resistor wire in these cars is inside the main engine wiring loom, and has a cover that is white, looks like a woven cloth cover, and travels from the bulkhead connector on the firewall (the engine side of the fuse box) to the positive side of the coil. It is 7 -1/2 feet long, silver stranded and carries a 1.80 ohm resistance value, same as the porcelain ballast resistors did in earlier days. the reason that wire is that long is, those cars were also available with an inline Chevy 6 engine, with the distributor on the pass side front of the engine, so, the resistance was figured into a wire that could work with either engine setup, rear coil, or, front coil.

Ignitors will not make any more spark plug energy, no matter the coil used, they don't have the electronic drivers to alter the dwell to store more energy in any coil, nor if a full 12 volts is used to over power them to their deaths.

I DO NOT RECOMMEND USING A RELAY TO POWER UP AN IGNITION CIRCUIT, JUST BEGGING FOR MORE PROBLEMS/ISSUES. 

Now, over the decades our cars have been in operation, things like corrosion and wire terminal degradation occur, and this causes voltage issues in most circuits. The bulkhead connector in the engine side is where the resistor wire starts, and its connector terminals could be very dirty, corroded, just plain not good. Take the connector off the fuse box, and take a serious look at the connectors. The factory put a grease on the connector, don't use too much of it, that will cause trouble as well. When dirty, these connectors can cause low voltage to components.

I do not know why anyone would want to use full battery voltage on a PerTronix Ignitor, or any Ignitor in the first place, but at full battery volts, it is just begging for Ignitor failures. 

If you insist on trying to murder the Ignitor, do yourself a favor, use a 12 gauge wire, from the coil positive post, along the wiring loom to the firewall near the steering column, and through it into the cab in a safe place, then, connect it to the IGN or IGNITION terminal on the fuse box. Take the resistor wire pair and tape them off, stick them into the over engine loom, so, if you ever do have to change back to a point set, in a month or two, the power for it will still be in place, and still functional. The IGN terminal should be "hot 12" in both start and run key positions, nowhere else.


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## BearGFR (Aug 25, 2008)

Umm... Dave... I'm doing that on my car because I'm running an aftermarket HEI (Davis Unified Ignition) that requires a full 12v for primary power. Installation instructions for the unit specifically state NOT to use the factory resistor circuit to power it. Running it through a relay as I did accomplishes the goal without requiring any modifications to the existing harness, and preserves the option of going back to stock if I ever choose to do that.


Bear


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## Dave Ray (May 18, 2018)

Bear, YES, full 12 volts is for all real HEI. IGN or IGNITION terminal on fuse box is excellent to power a good HEI up on "full 12". And, that is exactly what I said, stock ballast resistor wire stays in place and functional, only taped off and run down the loom. 

NOT for PerTronix Ignitor, they all need the ballast resistor in place and functional (this is from my own hands on testing and "fixing", which was the OP's ignition system discussion.

I've got 7, 55 gallon drums full with blown up Ignitors I have removed, and 99 percent of them were NOT the first Ignitor installed in that particular distributor. They were either warranty replacements, or, a second one installed after the owner was told they installed the Ignitor wrong.


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## rheckman (Aug 28, 2018)

BearGFR said:


> If you want the dead nuts easiest solution to running a non-stock ignition system that needs the full 12-volts to operate, then don't mess with trying to locate/remove/replace the resistor wire at all. Instead, get yourself a generic headlight relay from your local parts store. Mount the relay at a convenient spot near the ignition. (Mine's on the firewall) Disconnect the wire that used to go to the B+ terminal on the coil (the primary ignition wire that has the resistance in it) and instead connect it to the energizer circuit of said relay with the other terminal on that circuit going to a good ground. Wire the other side of the relay to a convenient full 12v source and connect the output of that from the relay to your ignition input. Problem solved. You now have full power to your ignition, and you didn't have to hack up your wiring harness to get it. If you ever decide to go back to 100% factory stock -- it's simple.
> 
> Bear


I came across this post looking for resistance wire bypass guidance and really like the idea of a relay.
But 2 questions,after taking off primary ignition wire you take that same wire and now connect to the relay?
And the last statement that says connect the output of that from the relay to your ignition imput.
What would the ignition imput be? Back to the coil?
Thanks


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## BearGFR (Aug 25, 2008)

Maybe this will help..

In my 69 I'm running an HEI. Normally HEI's are very simple - all they need is a constant 12v power supply to the +Batt terminal on the side of the distributor cap. The "other" terminal is there to provide a signal to a tachometer. 

On the original points ignition, the power source to the positive primary side of the coil "sees" a full 12v when the ignition switch is in the "Start" position, but in the "Run" position it gets switched onto a different feed that goes through a resistor wire. This all happens "inside and up under the dash" and is controlled by the ignition switch that's on the steering column (also up under the dash about halfway down the column). 

What I did was to disconnect the wire at the coil, and use it instead to trigger a relay. The relay doesn't "care" if it's being energized by a full 12 volts or is being energized by less voltage due to the resistor wire - it works either way. So on the relay, the original ignition wire is connected to the primary side on the relay (usually a terminal that is numbered either 86 or 85) and the "other" side (again 86 or 85) going to ground, such that when the ignition is on it will trigger the relay. On the "secondary" side of the relay (usually terminals are numbered 30 and 87 - I have no idea why they're different) -- one terminal goes to a full 12v source and the other terminal goes to the (new) ignition - the Batt+ terminal on the side of the cap in the case of an HEI. I'm pulling mine off a convenient unused terminal in the fuse block but it would work just as well going straight to the battery (if you do that, do include an in-line fuse between the relay and the battery for safety.

Does that help?


Bear


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## rheckman (Aug 28, 2018)

The new ignition,being the positive on the coil right


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## kobold (Jan 5, 2019)

Hello guys, I will install a Pertronix Flamethrower III in my 1968 Le Mans.
(hope, ideling will be a little bit better on my 400 engine with TriPower carb, 62 heads and hot cam...)
So, I have two questions:
Does the Pertonix III work with the original resistor wire on the coil or not ?
(I have already prepared a fused relais....)
Which springs should I use ? (there are three sets included, hard, middle, weak)
Which mechanical Limiter should I use ? (12°, 16° or 20° )
Regards: Peter


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## BearGFR (Aug 25, 2008)

Old Indian said:


> I have a 69 GTO with a Pertronix kit in the distributor but the voltage drops at RPM. I assume it is because of the ballast resistor or resistor wire between the run lead at the ignition switch and the coil. Can anyone tell me where the resistor wire is located? 68 and below had the ballast on the firewall. 69 changed when the ignition switch moved to the column, but I can't find the resistor wire in the shop manual.


There is a much easier way to solve this problem than trying to locate and bypass the resistor wire. 
Go to your local auto parts Big box store and buy a generic headlight relay. It doesn't matter which specific kind, anything will work. Get one that has 4 terminals: two for the triggering circuit and two for the triggered circuit. Disconnect the wire that feeds power to your coil and use that instead to trigger the relay. Run the other side of that primary circuit to ground, then use the secondary/switchef terminals of the relay to supply power directly from the battery to the new ignition system. Use nice heavy wire, like 12 or even 10 guage for this side, and include an inline fuse. Mount the relay on the firewall close to the coil. Another nice side effects with doing it this way is that if you ever decide to go back to stock it's easy because you will not have butchered anything on your wiring harness. This is the approach I used on my 69 and it works great. 

Bear


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## kobold (Jan 5, 2019)

Thanks Bear, 
as I said, I already prepared a fused relais, will mount it at an existing hole in the firewall.
What's about the settings for the Pertronix system, which adjustment is practicable / derivable for my engine ?
regards: Peter


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## BearGFR (Aug 25, 2008)

I know a lot of people seem to like the pertronix system. Personally, I'm running an HEI in my car. Specific settings as far as weights, springs, and advance curve are all going to be different for different cars. It depends on your particular engine build and even your geographic location/elevation. As far as timing, there are quite a few threads on this forum already about that, including some that I've written, talking about how to optimize timing for your particular car. The thread search tool can be your friend.

Bear


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## Lemans guy (Oct 14, 2014)

I agree with bear I run the relay on Petronix, and if call Petronix tech line they will tell you to do that. They recommend a full 12 volts to their unit, Petronix 2 and 3. Maybe some of the old ones it was a problem,...

but it needs a full 12 volts, that is what Petronix says, we know HEI does as well...

you can twist the ends of your two wires off the coil, the resistance one and the starter one, and hook them to a relay on the firewall. It will always give 12 volts at startup and run.....

also you don’t have to hack up, the harness so if you want to go back to points you can..

read your Petronix manual that came with the module, it will tell you it should be 12 volts, call their tech line.....

it works fine, I know Dave said he saw problems before, I believe that, but they new versions of these....


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## Lemans guy (Oct 14, 2014)

Ps the newer versions of Petronix do have variable dwell....a good feature


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## Pinexcorp (Jul 12, 2020)

geeteeohguy said:


> I've had 9 GTO's: all '65-'67's. NONE of them had a ballast resistor on the firewall. They all used a resistor wire to the negative side of the coil. Not sure of the resistance value, but charging system/batt voltage is dropped to around 9--10 volts. All the above listed cars were stock ignition, though. No pertronix. Hope this helps.
> Jeff


Hello Jeff I'm hope you can help me. I just bought a 1966 beautiful GTO that has been sitting for a long time I believe the car is all stock it has all its original wiring. My problem is with the resistor wire. I don't know if I really have a problem but I want to avoid a problem if you know what I mean. When I first got the engine started after replacing the fuel pump and other things I smelled something burning in and noticed that my harness was smoking. I quickly turn the car off and started to investigate what the problem might be. I determined that my resistor wire is running at a very high temperature. Is this a normal.? Their resistor wire which comes off the positive side of the coil is running so hot that I can only hold onto it for a few seconds. I have seen post here of people wanting to replace this wire but not because of it running at a high temperature but because they want to use a Petronix ignition. I want to keep my car stock but I'm not sure what to do about this wire. I guess my question really is do these resistor wires normally run this hot? Thank you for your response you sound like the guy that would know this since you had so many GTO's. Thank you in advance for your response.


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