# Ignition coil voltage



## greenjudge69 (Mar 8, 2015)

Hi guys. Im chasing.a driveability problem and I decided to check voltage at the coils POS terminal. My 69 has a freshly rebuilt stock distributor. I should have 12 volts during cranking, and about 9 volts with the engine running. I have 11.6 volts with the engine running. Trying to determine why. Don't want to burn the points out. Any thoughts? Thanks


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## armyadarkness (Dec 7, 2020)

To my knowledge, the only way that could happen is if your resistor wire, somehow stopped resisting. You can certainly test the wire by unplugging the connector at the bulkhead in the engine bay and then testing the ohms between there and the coil. You can buy new resistor wire or simply add a resistor. Accel Super Coils come with the resistor to add.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> To my knowledge, the only way that could happen is if your resistor wire, somehow stopped resisting. You can certainly test the wire by unplugging the connector at the bulkhead in the engine bay and then testing the ohms between there and the coil. You can buy new resistor wire or simply add a resistor. Accel Super Coils come with the resistor to add.


Thanks im going to check the wires coming from the ignition switch . Supposed to be one 12 volt lead for cranking, and another for running (9volts). There only one black/ pink wire for the positive coil terminal from the firewall connector.


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## armyadarkness (Dec 7, 2020)

greenjudge69 said:


> Thanks im going to check the wires coming from the ignition switch . Supposed to be one 12 volt lead for cranking, and another for running (9volts). There only one black/ pink wire for the positive coil terminal from the firewall connector.


These come with Accel coils... You can get them on Amazon. Also, if you look at your bulkhead connector or diagram, one top terminal is "Ign1" it's the resisted 9v wire in the engine bay, but a full 12v inside the car... So don't expect to test under the dash and find 9v anywhere. Ign2 is 12v at all times, but it's momentary, so when you stop cranking, it goes to Zero.

Here's a resistor


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## armyadarkness (Dec 7, 2020)

BTW, I can't imagine how a resisted wire couldve lost resistance, nevertheless, if that truly is your issue, and it's not due to something intentional, such as a distributor or other electrical mod that was made, then I would definitely replace the wire. Yes, adding the resitor I showed, or converting to a Pertronix module, will solve it, but it sounds like you have an unreliable circuit, so I'd be leary of trying to cheat it.

However, I've seen some incredible and amazing wiring techniques, in old cars. So, first make sure that someone didn't tap into the wire for a radio, fog lights, or some other silly thing, which should be reversed.

My 67 had the electric choke going to the windsheild wiper moter, the radio going to the horn, the aftermarket gauges connected with paper clips.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> These come with Accel coils... You can get them on Amazon. Also, if you look at your bulkhead connector or diagram, one top terminal is "Ign1" it's the resisted 9v wire in the engine bay, but a full 12v inside the car... So don't expect to test under the dash and find 9v anywhere. Ign2 is 12v at all times, but it's momentary, so when you stop cranking, it goes to Zero.
> 
> Here's a resistor
> View attachment 140335


Thanks for your help. This a real Judge and it would be difficult to hide that ballast resistor out of sight in the engine compt, so ill purchase a new resistance wire instead.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> These come with Accel coils... You can get them on Amazon. Also, if you look at your bulkhead connector or diagram, one top terminal is "Ign1" it's the resisted 9v wire in the engine bay, but a full 12v inside the car... So don't expect to test under the dash and find 9v anywhere. Ign2 is 12v at all times, but it's momentary, so when you stop cranking, it goes to Zero.
> 
> Here's a resistor
> View attachment 140335


Ok im confused. If both of the wires from the ign 1 and ign 2 terminals on the ign switch have to run through the resistance wire under the hood, . How do you get a full 12V to the coils pos post for starting when you put the key into the crank position? Thanks


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## integrity6987 (May 10, 2017)

greenjudge69 said:


> Ok im confused. If both of the wires from the ign 1 and ign 2 terminals on the ign switch have to run through the resistance wire under the hood, . How do you get a full 12V to the coils pos post for starting when you put the key into the crank position? Thanks


2 wires should be connected running thru the ignition switch - one supplies 12v during start. The other only 9v (via the resistor wire) in run. You will see this on the schematic.


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## armyadarkness (Dec 7, 2020)

greenjudge69 said:


> Ok im confused. If both of the wires from the ign 1 and ign 2 terminals on the ign switch have to run through the resistance wire under the hood, . How do you get a full 12V to the coils pos post for starting when you put the key into the crank position? Thanks


Sorry, you're simply not understanding. If you look at a schematic for your wiring, you'll see Ign1 and Ign2. They're two separate wires and bulk head connections. That's why the coil has two wires on it! Ign2 is only 12 volts when turning the key to start (momentary). The resistance wire is Ign1 and the wire itself is literally a resistor. So, inside the car, under the dash, the pink wire from the Ign1 portion of the key/ switch, would read a full 12 volts, because it doesn't get stepped down until it comes out of the bulkhead, in the engine bay. 

Does that make sense?


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## PontiacJim (Dec 29, 2012)

As pointed out, the resistor wire, usually a cloth cover wire, has a specific length and begins at the junction block on the firewall side, and then goes to the coil. Both wires, the "Start" and "Run" wires coming from the ignition switch to the junction block on the passenger side, are 12 volts at this point.

It seems a replacement resistor wire is not available and you may need to get one from a wire harness take-out and splice it into your harness coming out of the firewall.

Contact BLK69JUDGE as he may be able to help with a correct wire.

Maybe a Pertronix electronic conversion which needs 12 volts to work?


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## O52 (Jan 27, 2019)

And as mentioned, the cloth resistor wire is a specified length, usually 3-5 inches longer than it needs to be.


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## armyadarkness (Dec 7, 2020)

PontiacJim said:


> As pointed out, the resistor wire, usually a cloth cover wire, has a specific length and begins at the junction block on the firewall side, and then goes to the coil. Both wires, the "Start" and "Run" wires coming from the ignition switch to the junction block on the passenger side, are 12 volts at this point.
> 
> It seems a replacement resistor wire is not available and you may need to get one from a wire harness take-out and splice it into your harness coming out of the firewall.
> 
> ...


I wasn't sure about the resistor wire availability, which is why I had suggested the possibility of those Accel type resistors. It seems it would be easy enough to hide, but a pertronix module would be even better.


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## PontiacJim (Dec 29, 2012)

armyadarkness said:


> I wasn't sure about the resistor wire availability, which is why I had suggested the possibility of those Accel type resistors. It seems it would be easy enough to hide, but a pertronix module would be even better.


Yep, you could hide it, but the car is being restored to original, so not acceptable in this case. I'd go with the Pertronix as it isn't seen and really would not hurt value, but depending on the level of restoration and accuracy, it may not fit the owners desires.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> Sorry, you're simply not understanding. If you look at a schematic for your wiring, you'll see Ign1 and Ign2. They're two separate wires and bulk head connections. That's why the coil has two wires on it! Ign2 is only 12 volts when turning the key to start (momentary). The resistance wire is Ign1 and the wire itself is literally a resistor. So, inside the car, under the dash, the pink wire from the Ign1 portion of the key/ switch, would read a full 12 volts, because it doesn't get stepped down until it comes out of the bulkhead, in the engine bay.
> 
> Does that make sense?


Jim, the coil has one wire on the positive post, ( black-pink), and one black on the negative post for the points in the disriburor. Tharts all there is at the coil.


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## armyadarkness (Dec 7, 2020)

Well then I am very confused. I don't see how that could possibly be. There is no way that one wire wood supply two different voltages. Yes they could be joined somewhere else in the harness, but then the resistor wire would no longer function as intended. Are you actually burning points out? Maybe someone else has a different perspective but I think one of your wires may not have been reconnected when the distributor was rebuilt.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> Well then I am very confused. I don't see how that could possibly be. There is no way that one wire wood supply two different voltages. Yes they could be joined somewhere else in the harness, but then the resistor wire would no longer function as intended. Are you actually burning points out? Maybe someone else has a different perspective but I think one of your wires may not have been reconnected when the distributor was rebuilt.


I just checked voltage at the ign 1 and 2 wires on the ignition switch. The yellow wire is ign 2 and is only supposed to have 12v for cranking, but it has 12v in the run position? Should have zero in run position. The black pink ,ign 1 has 12 v in run as it should. Why is the ign 2 yelliow wire energized in run position is the major question. Only supposed to be hot in crank for starting??? Hmmm


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## AlaGreyGoat (Jul 6, 2006)

Some cars I have seen use this type circuit to the coil.
The wires off the switch run into the harness and are connected inside. The resistor wire is
usually a fluorescent color usually orange or green.
Starting, only the Start wire is energized and in Run, only the Run wire is energized
Check at the local auto parts store for a replacement resistor wire. They all should have
about the same resistance and should not be cut shorter.

Larry


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## PontiacJim (Dec 29, 2012)

greenjudge69 said:


> Jim, the coil has one wire on the positive post, ( black-pink), and one black on the negative post for the points in the disriburor. Tharts all there is at the coil.


OK, I pulled up what is supposed to be a wiring diagram for '69. Sure enough, only the single wire to the coil and the single wire to the distributor.

Pic 1 shows the coil/wiring. You can follow it up into Pic 2.
Pic 2 shows it as the Black-Purple wire running on the right of the diagram and going into the junction block on the firewall. It changes color on the interior side of the junction block and is now the Black/Pink wire.
Pic 3 shows the Black/Pink wire going into the ignition switch - keeping in mind that the ignition switch is on the steering column, not the dash.

Here is where I got the diagrams which I clipped the snippets from:



Wallace Racing - Wiring Diagrams



So my thinking is as the diagram shows, there is no resistor wire on the '69 A-body cars. I found this note, "A car that has the ignition switch in the steering wheel column and/or no inline ballast resistor (usually '69 and later)." Instead, a coil with the resistance already built in to it is used. Here is what I believe you will need for a coil to go with the single 12V wire set-up on the 1969 models.






Ignition Coil, 1954-74 GM, 3.25 Ohms, w/ Internal Resistor @ OPGI.com


Provide power to your ignition system with a new canister-style coil from OPGI. These replacement coils are a direct bolt-on for 12-volt applications without HEI ignition. Choose between internal or external resistor versions to suit your needs.




www.opgi.com


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## greenjudge69 (Mar 8, 2015)

Thank you!!! I believe you have solved the mystery. Ill either purchase the coil with the built in resistor and stay with the points/condenser, or go with the pertronix set up which i believe requires a 12 volt supply wire and my existing coil. Make sense? Just curious why i only have 11.6 V at the pos coil post with engine running and not 14.0 i have at the battery. All harnesses are new from M H except the dash harness. Its a very clean original 69 harness. Thank you all for your assistance!! Much appreciated.


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## armyadarkness (Dec 7, 2020)

PontiacJim said:


> OK, I pulled up what is supposed to be a wiring diagram for '69. Sure enough, only the single wire to the coil and the single wire to the distributor.
> 
> Pic 1 shows the coil/wiring. You can follow it up into Pic 2.
> Pic 2 shows it as the Black-Purple wire running on the right of the diagram and going into the junction block on the firewall. It changes color on the interior side of the junction block and is now the Black/Pink wire.
> ...


Nice find Jim. It really is amazing that so much of this critical information, is so hidden. It's scary to think about what others are doing, without this knowledge.


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## armyadarkness (Dec 7, 2020)

greenjudge69 said:


> Thank you!!! I believe you have solved the mystery. Ill either purchase the coil with the built in resistor and stay with the points/condenser, or go with the pertronix set up which i believe requires a 12 volt supply wire and my existing coil. Make sense? Just curious why i only have 11.6 V at the pos coil post with engine running and not 14.0 i have at the battery. All harnesses are new from M H except the dash harness. Its a very clean original 69 harness. Thank you all for your assistance!! Much appreciated.


So, did you change the coil to a non resisted already? Just curious. You mentioned drivability issues.

As for the voltage, it's gonna drop because there is normal resistance in the wire, plugs, and switches. I have been doing a lot of H4 headlight conversions and it's amazing how reduced the voltage is at the plugs, and once you fix that and supply it, WOW! The difference between 10 volts and 14 volts at the light, is amazing. I'm sure it matters with the coil, too.


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## Old Man Taylor (May 9, 2011)

armyadarkness said:


> Nice find Jim. It really is amazing that so much of this critical information, is so hidden. It's scary to think about what others are doing, without this knowledge.


All of us Old Timers had to do it all without all of this information readily available. That's why we know of so many problems. A lesson learned the hard way is one remembered forever.


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## armyadarkness (Dec 7, 2020)

Old Man Taylor said:


> All of us Old Timers had to do it all without all of this information readily available. That's why we know of so many problems. A lesson learned the hard way is one remembered forever.


I'm only 52, but I'm right there with you. My first 30 cars were wrecks that I had to figure out on my own, with nothing more than a Haynes manual and a lot of experiments. Plus, now that the web is here, personally, I find most of the information useless, because you can't verify the source, and there's more opinion than fact. Once I see any suspicious info... "Quadrajunks", then the whole source is contaminated!


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## 67ventwindow (Mar 3, 2020)

Wiring has always been a pain. I run a tone and trace out my wires, learned that from the wire dogs. Allot of places never had drawings of what went where. 
I grew up with people calling them Quadrajunks. late 70's and 80's engines were dogs and the parts houses always claimed a new carb and intake would fix everything.


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## O52 (Jan 27, 2019)

Ok I'm disagreeing. Reference is the 69 Factory Manual, Pages 6E20/21 and wire diagram, pages 12-6/7/8. Note the sequence table on the ignition switch schematic.

The Black/Pink Wire is the resistance wire from the ignition switch IGN 1 or E terminal to the B-Y terminal (interior side) of the firewall plug.
IGN 1 is the run circuit.

The yellow wire is the 12 volt wire which runs from the ignition switch IGN2 or D terminal to the B-Y terminal (interior side) of the firewall plug.
IGN 2 is the start circuit

Both circuits then run as a single wire from the B-Y terminal (engine side) to the coil.
This is a departure from 68 and before models where the resistance wire ran from the firewall plug to the coil in addition to the coil start wire.


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## O52 (Jan 27, 2019)

_I just checked voltage at the ign 1 and 2 wires on the ignition switch. The yellow wire is ign 2 and is only supposed to have 12v for cranking, but it has 12v in the run position? Should have zero in run position. The black pink ,ign 1 has 12 v in run as it should. Why is the ign 2 yelliow wire energized in run position is the major question. Only supposed to be hot in crank for starting??? Hmmm_

After reading this from the beginning I think your ignition switch may be bad energizing IGN 1 and 2 at the same time bypassing the black/pink resistance wire or...
it may need a simple adjustment up or down to isolate the two terminals from each other. Won't take much.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> So, did you change the coil to a non resisted already? Just curious. You mentioned drivability issues.
> 
> As for the voltage, it's gonna drop because there is normal resistance in the wire, plugs, and switches. I have been doing a lot of H4 headlight conversions and it's amazing how reduced the voltage is at the plugs, and once you fix that and supply it, WOW! The difference between 10 volts and 14 volts at the light, is amazing. I'm sure it matters with the coil, too.


My original coil was not on the car when i purchased it so i bought a non resistor coil thinking the wire in the engine compartment was a resistor wire. I just ordered a coil with the built in resistor. Then well see what happens. A little leary of the pertronix kits. I had one in my Hemi that worked fine but that was 10 years ago.


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## O52 (Jan 27, 2019)

Time for better glasses. I edited post 25 to correct the start circuit wire color


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## greenjudge69 (Mar 8, 2015)

O52 said:


> Ok I'm disagreeing. Reference is the 69 Factory Manual, Pages 6E20/21 and wire diagram, pages 12-6/7/8. Note the sequence table on the ignition switch schematic.
> 
> The Black/Pink Wire is the resistance wire from the ignition switch IGN 1 or E terminal to the B-Y terminal (interior side) of the firewall plug.
> IGN 1 is the run circuit.
> ...


Many thanks. You are correct. I spoke to the tech rep at [email protected] wire who i purchased my harnesses. He informed me that the resistance wire from the ign switch, ( black/pink) does take a few minutes to heat up and reduce the voltage from 12V to app 8.5-9.5. Ill recheck it soon after engine is warmed up. If its not down to the 8.5-9.5V, then i may use the coil with the built in resistor.


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## O52 (Jan 27, 2019)

You may want to verify the ignition switch first before swapping out the coil. With the battery disconnected, unplug the switch, turn the key to on (run) and check continuity between IGN 1 and IGN 2. Meter should show infinity. If you show '0' or very low ohms try moving the switch to obtain infinity. 
The truth table on the ignition switch schematic and the switch drawing show which terminals are used for every switch position.


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## armyadarkness (Dec 7, 2020)

Man... Lot's to learn, every day. I've been converting points to HEI and swapping coils, for more than 30 years, and I just found out about the resistor wire last year. Now I wish I could back to before I ever heard the word resistor wire! Life was bliss when I thought I had 12 volts.


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## O52 (Jan 27, 2019)

Fat, dumb, and happy huh? 😐

Unfortunately once you start tinkering with things you want to know WWWW lol.


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## armyadarkness (Dec 7, 2020)

O52 said:


> Fat, dumb, and happy huh? 😐
> 
> Unfortunately once you start tinkering with things you want to know WWWW lol.


EGGZACTLY! Which is why I get in trouble.


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## greenjudge69 (Mar 8, 2015)

O52 said:


> You may want to verify the ignition switch first before swapping out the coil. With the battery disconnected, unplug the switch, turn the key to on (run) and check continuity between IGN 1 and IGN 2. Meter should show infinity. If you show '0' or very low ohms try moving the switch to obtain infinity.
> The truth table on the ignition switch schematic and the switch drawing show which terminals are used for every switch position.
> 
> View attachment 140524
> View attachment 140525


I definitely have that on my list for Saturday. I was told by a tech at American Auto wire yesterday that the ignition switches from the current aftermarket suppliers are for chevys, and not the same as the original 69-70 Pontiac ignition switches . He stated that the original Pontiac switches drop power at the yellow ign. 2 start only terminal in the run position, unlike the aftermarket ones which would explain why i have 12v at the coil in the run position. According to him the replacement switches don't have the same configuration as the NOS 69-70 Pontiac ones which are unique . Of course no one sells the correct "69-70 Pontiac" switch anymore, but, I did manage to locate an original AC Delco NOS one just in case. He said he runs into this with the 69-70 Firebirds, GTO`s etc regularly. very interesting. thanks


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## O52 (Jan 27, 2019)

Wow, that's interesting and another bit of information fo my files.


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## greenjudge69 (Mar 8, 2015)

Update i ohmed out the terminals Ign 1 and ign 2 with the switch in " run" position and there is No continuity . That tells me the switch is operating correctly and that the voltage im seeing at the yellowwire, ign2, is feeding back from the bulkhead connection. I have 12.2 volts at the coil pos terminal engine running for 10 minutes. I believe the resistor wire from the ign switch to the bulkhead has failed. Im installing a coil with a built in resistor. Dont feel like cutting up my dash harness to replace the resistor wire. Thanks for all of your assistance.


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## armyadarkness (Dec 7, 2020)

greenjudge69 said:


> Update i ohmed out the terminals Ign 1 and ign 2 with the switch in " run" position and there is No continuity . That tells me the switch is operating correctly and that the voltage im seeing at the yellowwire, ign2, is feeding back from the bulkhead connection. I have 12.2 volts at the coil pos terminal engine running for 10 minutes. I believe the resistor wire from the ign switch to the bulkhead has failed. Im installing a coil with a built in resistor. Dont feel like cutting up my dash harness to replace the resistor wire. Thanks for all of your assistance.


Seems like a very unusual circumstance. I could see a resistor wire gaining resistance, hard to imagine it losing it.


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## armyadarkness (Dec 7, 2020)

In any event, you have many options to solve the issue, so that's good.


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## greenjudge69 (Mar 8, 2015)

armyadarkness said:


> In any event, you have many options to solve the issue, so that's good.


Yes i cant see how the switch is the problem based on my tests


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## armyadarkness (Dec 7, 2020)

greenjudge69 said:


> Yes i cant see how the switch is the problem based on my tests


Most of the repair jobs that I tackle are merely based on science and theory, because I work on hundreds of different machines, regularly. But most of the people that I meet here, have specific hands on knowledge of the task at hand. It's often hard to blend the two mentalities, but it's also very eye opening and rewarding. If it werent for the fact that my car didn't run right, I'd be really enjoying myself.


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