benito

1969 350/350 To complete my installation for max efficiencies the instruction say I need to remove the ballast resistor or remove the "resistance wire" from the circuit. I do not think I have a ballast resister. How do I find the resistance wire? The electrical diagram seems to indicate that it is on the driver side of the firewall.

Any help in locating this resistance wire would be appreciated. Once found, do I cut it out of the circuit by jumping it or remove it and splice the two wire ends together? Electricity is NOT my long suit.
Thanks!

69427

First, don't cut anything. There's more eloquent ways of getting the same result.

Going by memory there's two wires going to the coil C+ terminal. One has a cloth type covering over it (the ballast wire), and the other wire is the shunt wire from the starter solenoid. Unless I'm missing something here that the Pertronix module needs, neither wire needs to be removed. I would expect that you can just add an additional 12v wire from a switched source on the fuse block out to the coil C+ terminal to supply juice for the coil, and I assume to the module also.

I'm not a big fan of aftermarket ignition setups, so I welcome any corrections from those who have installed one of these units on their car.

CanadaGrant

I have a 69 with Pertronix. There are 2 cloth covered wires joined with a connector at the coil. One comes from the starter and the other is the resistance ignition wire. Don't cut or remove either one. Leave them connected. Just run an additional 12 gauge wire directly from the IGN terminal at the fuse box through the firewall to the positive at the coil. If you look at the firewall from the inside of the car or under the hood you will see a few carpet type plugs in holes up there. These plugs have a center hole in them except right at the end. Punch a hole through one and run your wire through it for a good insulator and attach the other end to the positive at the coil for a full 12 volts. You want to bypass the two stock ignition wires, not cut or remove them.

OldCarBum

Bypassing the ballast resistor by the above method works well. The reason the instructions are telling you to remove this wire or the ballast resistor is because the ballast resistor reduces the voltage at the coil from 12 vdc to approximately 10.5 vdc when cranking the engine. Old points systems are designed to supply the proper spark at 10.5 vdc and that is the reason the ballast resistors are in the system. The electronic ignition system you are installing needs 12 vdc during engine cranking to create the proper spark during engine cranking. I've seen where some people will install an electronic ignition system and not remove the ballast resistor from the system. The vehicle will start and run fine, however they have to crank the starter for longer periods and if the battery is weak or in extreme cold weather it won't start. You may think about replacing your coil to a non-resistor coil designed for modern ignition systems. A resistor type coil will work however it is designed for a points system with the reduced voltage.

MelWff

Actually the ballast resistor does the opposite of what OldCarBum stated, you get full current while cranking and then once started the power comes through the resistance wire.

benito

Thank you. Any idea on the location of the resistance wire?

69427

Please read post#2.

69427

Please read the Ignition Physics sticky here in C3 Tech. It corrects several old ignition wives' tales.

benito

Got it. I was just curious because I wanted the engine to look stock.

Thanks

CanadaGrant

The reason I leave the two cloth covered wires connected is because as part of the stock under hood wiring harness, I might want to use them again with the stock points. I sure don't want to cut them off and I don't want to leave live wires hanging there so why not just leave them connected properly where they are supposed to be? All you are doing is plugging in one 12Ga. full 12V wire from the fuse box IGN terminal to bypass or parallel the resistor wire so it looks fairly stock unless you really know what you are looking for. As said by OldCarBum, the Pertronix unit will run fine using just the ballast resistor wire but in cold weather or with a low battery you will be out of luck starting it so you need the full 12 volts. I know of one person who ran his C3 for over a year off the ballast resistor wire with no problems but that really isn't the way to do it.
The 2 cloth wires are joined at a common connector at the coil. The one that goes from there down to the starter supplies a full 12 volts directly from the starter to the coil when the key is turned to the "start" position ONLY. The other similar looking cloth covered wire joining that one at the coil is the ballast resistor wire.

OldCarBum

This is the same issue I had with a classic Mastercraft boat I restored two years ago. I was having to crank the motor longer than what was normal and after a few cranks it would not start. I replaced all battery cables, the ignition switch, starter relay, starter and solenoid. The prior owner had switched the points over to Pertronix electronic. I contacted their customer service and explained the problem with the voltage drops I was seeing at the coil while cranking. Their technician told me to bypass or remove the ballast resistor from the ignition system and advised me to replace the coil with a non-resistor coil. I did as instructed and afterwards I just touched the key and the motor fired instantly every time. It is a good system and has never given me any troubles. Good luck.

7T1vette

You get full voltage to the coil when cranking because that voltage is coming from the starter solenoid (S terminal)...not from the ballast resistance wire. After the engine is running, the coil power comes through that resistance wire. Also, that wire is there to limit current flow to the coil so that points won't burn and coil won't fry.

Now to your situation: Trace back the coil wire that comes from the bulkhead connector at the firewall (that wire is the resistance wire). Do not cut that wire; just tape off the connector, roll it up and use a tie-wrap to retain it on the firewall somewhere. Then, if someone ever wants to return it to 'stock' condition, they can.

Instead, tap into that wire immediately outside of the bulkhead connector, and run another wire from that tap to the coil. That will send an 'unrestricted' 12 vdc to the coil for the Pertronix.

69427

Why?

benito

EXCELLENT! Thank you.

WESCH

Hi

The reduced voltage via the resistor is for the coil.
Early coils are build for 10V and fry if operated too long at 13 V +.
Hence, it depends on the coil you're using if you should retain the resistor or not.
I'm running Pertronix 1 since 2002 with the resistor because I kept the coil, did not use the Pertronix coil.
The Petronix itself is just a switch, like the old contacts.

At least this is how I understand the system.

Rgds Günther

benito

I purchased the Pertronix (Flame Thrower) coil that was recommended with the electronic points. The Pertronix instructions recommended bypassing the resistor wire for max performance but it is not necessary. Its all making sense to me now. Thank you.

ddawson

If you want to go a different route and use only the resistor wire check out the http://www.breakerless.com/

Unlike competitive systems though, no additional wires protrude from the distributor, only the original points wire.

I used this along with an Accel coil and it's been find for years.

Dino_'72

Benito, which Pertronix version are you using? Some need 12V constant ignition source.

I recently installed the newest Pertronix III version on my '72, it's needs constant 12V ignition source after start up. So no more resistor wire needed.

My 67 Impala has the older Pertronix I unit (different design), it runs off the resistor wire no problem.

Dynra Rockets

I installed the Pertronix III in my '69 a few years ago (5 years?). I knew about the voltage drop from the resistance wire working on cars of this era as a kid but read online that as long as it was getting over 9v the PIII would still work. After installing it seemed to work fine with the resistance wire as-is.

Fast forward to this past fall and the original 48 year old starter died. I ended up installing a modern light weight starter (easily a 5 lb reduction) which did not have provisions for the R wire that provides the higher cranking voltage back to the coil.

I decided to remove the resistance wire from the system altogether and run a whole new wire from the firewall junction block to the coil. I found a box of NOS type 56 brass locking blade terminals on ebay (the current auto store tin plated Dorman stuff I thought was junk) and changed out the whole resistance wire by replacing it in the terminal block. My car is more of a restomod anymore so not worried about originality.

Was it a pain to do? yes, but not awful and I feel better that there is a fresh wire in the harness and not a 48 year old cloth wrapped piece there. The best part is the PIII with full voltage makes the car start and run much better. I didn't realize what I was missing.

benito

Thank you. Great info.