# HEI 12V source



## 67lemans (Oct 30, 2009)

I've read several threads that say I need a full 12V both during cranking and during run time, but I'm sorry I didn't see where you were going to get that? 

I'm sure its been covered and I just didn't catch it. Thanks. (67 lemans 326 and it was formerly a coil and points - engine now out so I can't test voltage yet)


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## PontiacJim (Dec 29, 2012)

You can run a wire right off the key/ignition switch and bypass the resistor wire, but keep the resistor wire in place should you ever want to go back to points or should you sell the car and the next owner wants original.

It has been said that the resistor wire goes from the coil to the firewall wiring box, then a standard 12V wire on the other side of the box goes to the key/ignition switch. One member said he eliminated the resistor wire and simply wired a standard non-resistor wire to the pin in the wiring box so it looked factory. This would mean separating the firewall wiring box and then doing a little surgery.

Your other option would be a toggle switch to divert 12 V to the coil. Again, remove the resistor wire, wrap the end in electrical tape and tuck it out of site should you ever want to use it. Then simply run a 12V sourced wire to one side of the toggle switch and back out to the coil. You could hide the toggle switch so no one could start the car unless the switch is "ON." Just have to remember to turn the switch "ON" when you crank the key - or the engine will fire and die as soon as you let the key go. If you want to get fancy, get one with a light that lets you know the switch is "ON" so when you turn off the car, you don't forget the switch is "ON" and could fry the electronics. I would also wire in an inline fuse on the 12V power side just to protect things. Make it accessible incase you have to replace it. They have mini fuses out now that will light up (LED) when the fuse blows, so real easy to check by site - if it is lit, it is bad.

So that is just a couple ways to do it. Not too hard.


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## 67lemans (Oct 30, 2009)

Thanks for the quick thorough reply Jim. That gives me some options. 

If I go off the ignition switch, I think that would give me 12V during both cranking and running. 

If I replace the resistor wire (which wouldn't be so bad with the engine out), I still would still need to use the wire from the starter so that I have 12V during cranking.

Do I have that correct? Thanks, DD


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## Mine'sa66 (Oct 30, 2019)

You took out the points distributor and replaced it with a stock type HEI distributor? Remove the resistor and use that wire as the wire that goes to the distributor. Don't have the diagram, and if a 66=67, but IIRC The wire that goes down to the starter is factory spliced in the harness. I would just leave it and use the other wire w/o the resistor. You'll need a tach filter to run a factory tach off the HEI.


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## 67lemans (Oct 30, 2009)

Yes. 

I think this is becoming more clear. The resistor wire has power during cranking, as well as during running, it's just that it's 8-9 volts? So if I replace the resistor wire (or remove the resistor) I don't need a second wire from the starter to have power during cranking. Is that right?


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## 67lemans (Oct 30, 2009)

I will preserve the resistor wire for the next person in case they want to go back to points.


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## PontiacJim (Dec 29, 2012)

67lemans said:


> Yes.
> 
> I think this is becoming more clear. The resistor wire has power during cranking, as well as during running, it's just that it's 8-9 volts? So if I replace the resistor wire (or remove the resistor) I don't need a second wire from the starter to have power during cranking. Is that right?


No, I don't think the resistor wire has power when you initially crank the engine, but I have never tested for this, so it might. When you turn your key to "Start", there is 1 wire that sends 12 volts to the coil to provide a good hot shot of 12V that fires up the engine. When you snap the key back to the "Run" position, the 12V wire is no longer active/live, and power is then diverted to/through the resistor wire attached to the coil. The resistor wire drops voltage don to 7-8 volts so as not to burn up the points.

So you cannot "Run" off the 12V wire running from the key to the coil because it is no longer powered once you snap the key from "Start" position to the "Run" position. So you have to provide a 12V source that is live when the key is in the "Run" position, and not the 7-8 volts the coil will see using the resistor wire.

The simple version - Inside the key switch is a series of contacts. The contacts are energized by the position the key is turned in the switch. On the back side are the contact tabs that your harness plug goes into. Then depending on how the key is turned, the contacts in the switch direct power along the wiring harness to where it is needed, ie starting the engine.

So look at your coil + side. You should have 2 wires. They may be separate wires or joined together with a common end, I can't remember. The wire having what appears to be a cloth covering is the resistor wire. If not sure, you can cut the wires, then with a light tester, turn your key to the "Start" position and the test light will light up - letting you know this is your 12V "Start" wire and the other wire will be your resistor "Run" wire.

Then you can go from there in how you want to do a work around to eliminate the resistor wire and replace it with a 12V wire that provides 12V when your key is in the "Run" position - either through your wiring harness, your key switch, off a toggle switch or.........


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## 67lemans (Oct 30, 2009)

That clears it up. I was just confused about getting 12V during crank. My 2 wires do come together in a single spade at the coil + terminal and one wire is cloth covered or "furry"(after 50 some years). I'll double check the voltages, but I can easily preserve the furry wire for future, and find a 12V source in the key "on" position. Many thanks! 

Next up, wiring the lock up converter!


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## Mine'sa66 (Oct 30, 2019)

67lemans said:


> That clears it up. I was just confused about getting 12V during crank. My 2 wires do come together in a single spade at the coil + terminal and one wire is cloth covered or "furry"(after 50 some years). I'll double check the voltages, but I can easily preserve the furry wire for future, and find a 12V source in the key "on" position. Many thanks!
> 
> Next up, wiring the lock up converter!


Yes, basically you're leaving everything as it is except you will not have a resistor in the run circuit.


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## Lemans guy (Oct 14, 2014)

Here is another easy and very reliable way. Get a four pin, (some have 5 one you won’t use)
12 volt relay at any auto parts store. Screw it to the firewall near the coil.

take the two wires that are going to your positive coil, if they are on one spade terminal, leave them that way and stick them on the terminal for the switch input on the relay.

the other side of the relay pin just run to ground, you can put another screw in firewall.

then from any reliable 12 volt source, that is on at crank and run you connect to one of the relay power terminals, and the other relay power terminal goes to the coil positive.

The main wire and resistor wire then just close the relay, and at crank and run a full 12 volts to the coil. The reason this is reliable is that the relay only takes about 6 volts to close and 1.5 volts to stay closed. So even if you have resistance from an old wire somewhere between the relay and the switch it still cranks up and runs great.

you can also carry a spare relay, but they rarely fail and are inexpensive.

you could grab that 12 volt power from the line that goes from the alternator to battery to charge it. Any reliable source that is 12volts during crank and run.

if you want to go back to pointsjust unhook to the relay and go back direct. No hacking up stuff if you don’t want to get into the harnesses too deep or the firewall fuse box.


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## O52 (Jan 27, 2019)

Take a look at your fuse box and see if you have an IGN or IGN FUSED terminal. it will be in line with the BAT and ACCY Terminals. That terminal is your 12 volt ignition feed when running. I ran a 12 gauge pink wire from there to my coil for a Pertronics III set up on my 70 El Camino. 

Your fusebox will be physically different from the photo but will have similar terminals


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## 67lemans (Oct 30, 2009)




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## 67lemans (Oct 30, 2009)

Per the service manual:


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## 67lemans (Oct 30, 2009)

PO has pink wire going to electric choke.


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## RockyIce (Jun 2, 2018)

So I'm interpreting the above that you can take power for the HEI from Fuse Box? I've just installed a repro harness and need to figure out the 12V for HEI. I can easily run a wire along firewall to Fuse Box. Just confirming there is the right Run source of 12V to connect to there. 1964 GTO.
Ideally, I don't want to cut anything or alter any of the harnesses. Just run a wire and plug and play if this is truly an option.


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## Mine'sa66 (Oct 30, 2019)

RockyIce said:


> So I'm interpreting the above that you can take power for the HEI from Fuse Box? I've just installed a repro harness and need to figure out the 12V for HEI. I can easily run a wire along firewall to Fuse Box. Just confirming there is the right Run source of 12V to connect to there. 1964 GTO.
> Ideally, I don't want to cut anything or alter any of the harnesses. Just run a wire and plug and play if this is truly an option.


The HEI doesn't care where it comes from, you just need to grab it from anywhere you get 12v in the "run" position.


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## O52 (Jan 27, 2019)

If your fuse box doesn't have an IGN terminal, they can be easily added.


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## 67lemans (Oct 30, 2009)

I was able to replace the resistance wire tonight. Spliced the new wire in with the "starter" wire from before, and left the resistor wire, so I should be good. I wired the starter up in the engine bay to check everything was good. Thanks so much for the ideas. I'm wanting to get these little things done before I drop the engine back in.

I really liked the relay idea Lemans Guy had with the relay. I'd probably do that if this didn't work.


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## BearGFR (Aug 25, 2008)

Easy to do, and you don't have to hack up your wiring harness to do it. Grab a generic headlight relay from your local parts store, mount it to the firewall in a convenient spot near the distributor, and make the connections.


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