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Does Pertronix Ignition Require Resistor Plugs?

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Oldwrench View Drop Down
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    Posted: 28 May 2023 at 7:06am
I installed a new set of points and condenser on my D17IV as part of a routine service, only to have the condenser fail big time after only a few hours of use.  The condenser was a Blue Point.  So after 45 years of reliable running on points, given the lousy ignition parts available today, I decided I had enough, and am installing a Pertronix kit on it.  I prefer a simple points/condenser, but unreliable parts has made them not worth it anymore.

Quick question that I can't seem to find information on in the Pertronix site.  Do I need resistor plugs or a resistor plug cap?  The instructions explicitly require carbon plug wires, which I purchased along with the unit.  However, no mention of resistor plugs.  Although not related, I know when switching to a solid state ignition on other older vehicles, such as my 1970 Triumph, a resistor plug or a plug cap (but not both) is required to prevent interference with the transistors of the ignition unit.  Do the carbon wires of the Pertronix function as resistors?  Or does the Pertronix not need resistors?  I will purchase new R type plugs if needed, but no mention of them in the instructions.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DrAllis Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 7:59am
Don't think so. Funny thing about the current Pertronix electronic ignition systems. I have a WD45 that has an 11 year old Pertronix ignition system and NO MENTION of resistor wires at that time. No mention of resistor plugs either. I put 50 hrs a year on it with no problems whatsoever. When I installed a new Pertronix kit in my One-Seventy this past winter, now they demanded resistor wires ! but no mention of the spark plugs. So, what has changed in 11 years of production ????????
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PaulB Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 8:21am
The short answer is NO.  However if you buy a new Petronix kit today, It does require Resistor wires. The older units worked just fine with standard plugs and solid copper wires. There was a change in the electronics a few years ago and using solid copper wires on a newer unit will cause a new unit to fail.
  Also something to consider; using resistor plugs will result in more precise control of ignition timing. The resistor act as a pressure valve and will not let the plug fire until a set amount of voltage has reached to plug,  resulting in a hotter spark at a more precise time.  With a standard plug it will spark at any time that it has received sufficient voltage to jump the gap at whatever the current conditions are.
If it was fun to pull in LOW gear, I could have a John Deere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote darrel in ND Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 8:29am
I put a pertronix on my one ninety gas 15+ years ago and ran it with the original plug wires until this last winter.
The original pertronix gave up, and when got a new one, the instructions very clearly required rosin core (not sure what rosin core means vs carbon filed) plug wires. Put in new plugs, the rosin core wires, and the new pertronix and it runs like a champ again
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldwrench Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 8:36am
Thanks Doc and PaulB.  I have been reading up on this topic and am learning a lot.  One thing it seems is that resistance in the ignition circuit reduces the current but does not change the firing voltage, which is fixed by the plug gap and combustion chamber pressure.  So reducing the current and the resulting inductance and RF signals for a solid state trigger device makes some sense.  It also makes sense that the newer Pertronix may not like handling the higher current of an older conventional system.

Not to complicate things, as I will use the carbon wires Pertronix supplied, but if I wanted to use solid core wires (for physical robustness and reliability) could I use resistor plugs instead of the carbon wires and accomplish the same thing?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Les Kerf Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 9:32am
Utter nonsense.
If you are using the same coil there will be absolutely no difference whatsoever in either the spark plug or or plug wire requirements or performance. The Pertronix is merely a solid-state switch which replaces the mechanical breaker point switch.

If you switch to a 'hotter' coil having a lower primary resistance (a silly thing to do on a stock Allis-Chalmers tractor) you stand a good chance of burning out a Pertronix.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Les Kerf Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 9:45am
Originally posted by Oldwrench Oldwrench wrote:

...

Not to complicate things, as I will use the carbon wires Pertronix supplied, but if I wanted to use solid core wires (for physical robustness and reliability) could I use resistor plugs instead of the carbon wires and accomplish the same thing?


While not necessary (please read my post above) there is also no harm done by running resistor wires and/or resistor plugs. Your combination of solid core wires with resistor plugs will work just dandy, and your AM radio will too.

Listen folks, the resistance of the air gaps in the distributor rotor plus the air gap at the spark plug is in the order of several Mega-Ohms while the combined resistance of the resistor wires and plugs in only a few Kilo-Ohms, which in the grand scheme of the cosmos is truly insignificant. Please do not allow advertising hype to cloud your thinking.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote PaulB Quote  Post ReplyReply Direct Link To This Post Posted: 28 May 2023 at 7:19pm
Originally posted by Les Kerf Les Kerf wrote:

Utter nonsense.
If you are using the same coil there will be absolutely no difference whatsoever in either the spark plug or or plug wire requirements or performance. The Petronix is merely a solid-state switch which replaces the mechanical breaker point switch.

Les: do you wish to back up your statement and pay for anyone's New petronix conversion that fails when used with old style copper core wires???  I doubt it.  If the instructions include the statement "Warranty is VIOD if used with solid copper wires"  Why would anyone be so hard headed as to use copper spark plug wires? I'd believe that the Petronix company that has years of research and development  knows their product 
If it was fun to pull in LOW gear, I could have a John Deere.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote JPG AUSTRALIA Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 12:16am
Les is right,electronic ignition is just a switching device,but maybe they now have been using cheaper components that dont like the rf interference,most things made today cant handle any slight magnetic field. They are just covering themselves like every company does nowdays so they dont have to be responsible for inferior products. Old electronics used robust transistors that would just about handle an arc welder right next to them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Les Kerf Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 6:55am
Originally posted by PaulB PaulB wrote:

...  Why would anyone be so hard headed as to use copper spark plug wires?

I do. On my Pertronix-equipped Model C

Originally posted by PaulB PaulB wrote:


I'd believe that the Petronix company that has years of research and development  knows their product 


Having personally spent years in the engineering department of a major industrial encoder manufacturer doing research and development of the electronics systems for those encoders I am very confident that Pertronix is merely weaseling out of warrantying anything they can possibly weasel out of.

I do happen to have a degree in electronics engineering in addition to 40+ years of experience in military avionics, industrial systems, and Bio-med.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote darrel in ND Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 8:06am
After this thread, I would really love to see Les and the pertronix engineers in the debate ring together, get the matter settled once and for all. Even though I did follow like a sheep and use the rosin filled plug wires like pertronix requested, Les's arguments, knowledge and experience ad up to the notion that maybe pertronix can weasel out of warranty. But I still have to think that there may be some integrity backing up the request for the rosin core wires. I'm definitely not being derogatory towards anyone, utmost respect for everyone's thoughts on the matter. Darrel
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Codger Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 8:11am
Consumer electronics are built with cost containment as a driving factor extensively. It's the reasoning some components or items last, and some don't. You can build it very robust, but can you then sell it? The competition is always out to undercut for market share or sales. Some consumers justify the $$$ for a quality product, most only go by the lower price perspective.

I've never had a "Pertronix" unit myself but know several that have installed them and been happy. Some however have not been happy. Twice I know of the full ignition system has not been evaluated and the "Pertronix" unit blamed. Both of these needed the actual distributors rebuilt as the electronics require a stable input to output correctly and a worn distributor shaft and/or bushings are not stable mechanical inputs. Another was quite possibly a backfeed issue to the "Pertronix" unit burning it out. A replacement MSD ignition coil cleared this problem, but was not original in appearance.


Edited by Codger - 29 May 2023 at 8:12am
A career built on repairing and improving engineering design deficiencies, shortcomings, and failures over 50 years now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldwrench Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 8:38am
I installed the Pertronix yesterday and cleaned up some old wiring, eliminated the ballast resistor, etc.  Straightforward job with no issues. I also used the recommended carbon, rosin, silicon... whatever core wires from Petronix with the non-resistor plugs already in the motor.  I also installed their 3 ohm coil.  It had 2.8 ohms on my meter, so close enough.  It started right up instantly, like normal. 

I have a question on the timing.  It has a loader on it, but using a small hand held mirror as others have recommended on this site, I could flash into the timing hole and see everything pretty well.  I used a separate battery to power the timing light.  At high idle, the timing mark comes into view. But it is not stable, and moves back and forth a fair bit, but remains within view within the diameter of the hole.  The engine speed is stable.  When I installed the Petronix, I could not feel any play in the distributor shaft.  I did not do anything to the advance mechanism, but it worked smoothly and the shaft would advance maybe ~ 5 deg when I manually moved it. The advance also works as it moves the timing mark into view as I throttle up to ~ 1600 rpm from idle.

I'm wondering why the timing mark is not rock stable in the hole?  On average, it is pretty much centered, so the Pertronix didn't change the timing.  I haven't checked the timing for quite a while, just changing points over the years, so I don't know if this is new or not.  I guess I would suspect a worn distributor shaft, although I can't feel any freeplay moving it manually side to side.  The Pertronic plastic cap fit snugly onto the shaft.  How stable should I expect the timing mark to be?


Edited by Oldwrench - 29 May 2023 at 8:40am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Codger Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 9:08am
Much of that believe it or not is the circuitry in the timing light itself. It takes a while to build charge to flash the strobe and as electronic components, (usually capacitors) age, they still work but lose some linearity of charge meaning the strobe output is erratic.

A worn gear on the bottom of the distributor shaft, or camshaft itself is also a player as is the oil pump drive in some engines. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldwrench Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 10:15am
Codger,

Good point.  I didn't think of the light itself.  It was a brand new Sears one back around 1960 or so, and I was so proud of getting a real light rather than the dim red neon things from Western Auto.  I'll try another light, as I'm guessing mine is out of warranty by now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Les Kerf Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 11:18am
Originally posted by Oldwrench Oldwrench wrote:

...  How stable should I expect the timing mark to be?


It will not ever be very stable on these old tractors. The timing mark is on the flywheel, which is solidly attached to the crankshaft. The camshaft is geared to the crankshaft and there is always some backlash, then the magneto/distributor drive is geared to that; a magneto drives straight on but the distributor adds a worm drive into the mix. Now put 70+ years of wear on an already sloppy mechanical drive and you will get what you see. If it runs to your satisfaction don't sweat the petty stuff.

All of my previous statements apply to a stock-type coil only, as in you were running a stock ignition system and swapped out the breaker points for a Pertronix; change to a different type of coil and all bets are off, it may be fine and maybe not.

I am retired from Encoder Products Company, the units we built were all produced to ISO standards, we did Shock & Vibration testing, ESD testing, we ran them at 120 Degrees C for 1000 hours and another 1000 hours at -40 C (yes, the very same units) all at maximum rated RPM. Our encoders were warrantied for 3 years in industrial use, our closest competitors only had a one year warranty. I was intimately involved in testing failed units that had been returned by customers; we had a very low failure rate and most of the returned units (80%) were due to improper connection by the customer.

When you have access to an Electron Scanning Microscope you can see right down to the nitty-gritty of what really happened inside a transistor and why.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Steve in NJ Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 1:11pm
We're a Pertronix dealer and a few years back, Pertronix was trying to figure out why their modules were blowing out especially in Tractor appliciations. According to their bulletin back then, they finally figured out with quite a bit of R&D if using a solid core wire, a stray spike could blow the module out. This is when the bulletin said that anytime selling an E.I. to a customer, make sure the vehicle is NOT equipped with solid core wires. Make sure the customer installs carbon core wires which will stop the stray spikes the solid core wire can give off especially in humid or wet weather/days. From what I understand, since using the carbon core wires, Pertronix E.I. failures were cut way down big time. You don't need to run resistor plugs with the carbon wires....  HTH
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jgranat Quote  Post ReplyReply Direct Link To This Post Posted: 29 May 2023 at 3:55pm
I have a Pertronix on my CA with a Flamethrower Brand 12 volt coil, copper wires and non resistor plugs. It mows 2 acres every week, always starts. 10 plus years now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SteveM C/IL Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 9:27pm
Originally posted by Jgranat Jgranat wrote:

I have a Pertronix on my CA with a Flamethrower Brand 12 volt coil, copper wires and non resistor plugs. It mows 2 acres every week, always starts. 10 plus years now.

Reminds me of Dirty Harry line...Do you feel lucky?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote steve(ill) Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 9:45pm
Make sure the customer installs carbon core wires which will stop the stray spikes the solid core wire can give

almost all tractors at one time had copper core wires.. Im not sure why there would be " stray spikes" unless the copper wires were 30 years old and hard / cracked... I wonder if that was he problem, just OLD WIRES.. If you go to NEW carbon, there apparently is no problem... If you go to NEW COPPER, that might also solve the problem ??
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Post Options Post Options   Thanks (1) Thanks(1)   Quote DaveKamp Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2023 at 11:03pm
The two simple reason for their direction to use resistor wires, is specifically for suppression, as the result of HF ringing finding it's way backwards into the Per's switching transistor WILL cause a very high RF voltage to appear along that line... and while they're tough,  won't always kill it, it will SOMETIMES kill it... and the other silly side effect, is that inductance is phase shift, the transistor is an amplifier, and the presence of a signal coming backwards is feedback... and these things in combination constitute an oscillator... at least, until the semiconductor emits magic smoke.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jgranat Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2023 at 4:41am
Originally posted by SteveM C/IL SteveM C/IL wrote:

Originally posted by Jgranat Jgranat wrote:

I have a Pertronix on my CA with a Flamethrower Brand 12 volt coil, copper wires and non resistor plugs. It mows 2 acres every week, always starts. 10 plus years now.

Reminds me of Dirty Harry line...Do you feel lucky?


Lucky I don't have points, condensor, or coil issues? Yes.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote PaulB Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2023 at 6:37am
Originally posted by Jgranat Jgranat wrote:

I have a Pertronix on my CA with a Flamethrower Brand 12 volt coil, copper wires and non resistor plugs. It mows 2 acres every week, always starts. 10 plus years now.
 If your unit is 10 years old, you won't have issues.  The problem is with NEW units that have been made in the last few years (I'm thinking the change came about in 2019 or so). I also have units that I have had for 20+ years and the copper core wires have worked just fine. However any NEW unit I get now will only get suppression wires as per Petronix instructions. If you get a NEW unit read the instruction and warranty information.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Les Kerf Quote  Post ReplyReply Direct Link To This Post Posted: 31 May 2023 at 9:12am
One more story and then I will stop.

The last sawmill I worked at installed a new end-dogging overhead log carriage that had a pressure transducer  to signal when the log was securely clamped; we had numerous transducer failures and the supplier kept blaming EMI, shock, vibration, the phase of the moon...  etc. I told the sales rep the story about how during WW2 they developed the proximity fuse for artillery shells using vacuum tube technology; these fuses could withstand the forces of literally being fired from a cannon. Of course they only had to work one time, but the folks on the receiving end were of the opinion that they were too reliable.

We switched to a different brand of transducer from another supplier and our problems went away. The moral to that story is sometimes there is a significant difference in quality.

Some of the encoders we produced at my last job are used in government contract stuff, they used special components (expensive). I can't say any more about those.

Originally posted by DaveKamp DaveKamp wrote:

The two simple reason for their direction to use resistor wires, is specifically for suppression, as the result of HF ringing finding it's way backwards into the Per's switching transistor WILL cause a very high RF voltage to appear along that line... and while they're tough,  won't always kill it, it will SOMETIMES kill it... and the other silly side effect, is that inductance is phase shift, the transistor is an amplifier, and the presence of a signal coming backwards is feedback... and these things in combination constitute an oscillator... at least, until the semiconductor emits magic smoke.


Agreed.
Ignition systems make high voltage spikes on purpose. Using cheaper components is sorta like me getting into the ring with Joe Frazier and saying "Please don't hit me!" Tongue

I just wish I could find reliable condensers nowadays, that's the only reason I switched to Pertronix.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaveKamp Quote  Post ReplyReply Direct Link To This Post Posted: 02 Jun 2023 at 9:54pm
Originally posted by Les Kerf Les Kerf wrote:

I just wish I could find reliable condensers nowadays


AMEN!!!!


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