Oscilloscopes...

[The Chairman]

We can lead you further afield without much difficulty (grin). Just ask!

It was such a huge portion of my life and identity for 30+ years, that it's nice to reminisce with fellow cam-heads. The field has changed drastically. Where I used to be able to go out to a car with a medium slotted screwdriver to suss things out and adjust many things by ear, it's no longer the case. I still poo-poo people when they say cars are too hard to work on anymore. The grey matter between your ears is still the most important diagnostic tool in your repertoire, but the various inexpensive analyzers and code readers make things quite easy.

 

[TrimixToo]

That's a DIS system and not a points system.
The cap here is on the supply side, on points, it's on the ground side of the coil.

“Since it’s on the power feed side,​

When the points open the coil (transformer) primary field collapses, inducing amplified volts on the secondary side. The greater the capacitance, the longer the duration of the spark. V-8s need lower capacitance than a 4, just as the dwell (point gap) is also smaller. If the gap is not sufficient, then there is a possibility that the cap will not fully discharge. Too brief of a spark and you might not light the fire. You can always run a v-8 cap in a 6 or 4, but not necessarily the other way around. While carb issues can affect the strength of the spark, they don't affect spark duration. Best practices are set the dwell, then the time, check for proper spark advance and then adjust carb idle. I have no idea how many hundreds of points systems I had to diagnose and repair. I've heard all sorts of whacky ideas from them being a "false ground", to... well it's been a long, long time. On most cars, dwell was set with the distributor cap and button off. GM had little windows in the distributor caps you could slide up and insert an allan wrench to adjust it while idling. Damn, I think it was GM (AC-Delco). I was almost exclusively imports until the mid 80s. By then, points were starting to become rare. More and more, my fellow auto-technicians had never installed points, changed out a generator, or truly relined a set of brake shoes. Slapping on a set of rebuilt shoes doesn't count. Most had no idea what the first emission control device was, and had never rebuilt a fuel or water pump. They had become effing parts changers.

Little known fact: except for the 009 (Porsche or racing) distributors, VW retarded the 3rd cylinder to keep the heat down. It was important to match that retarded electrode accurately, or possibly burn the #3 piston exhaust valve. If you installed a 009 distributor, be sure to retard initial timing a degree or two.

There were *two* links there. Did you read the first? I included the second because it was very clear about what was happening as the fields collapsed.

It's the higher voltage temporarily induced by the field collapse in the primary coil that's at issue when it comes to sparking across the points and causing premature erosion. It's that energy that has to be stored, and it gets released once the field collapses enough. Once the points are far enough apart, there is no need to store the energy. Yeah, that might make the spark last longer, but I'm not sure that's meaningful in the grand scheme of things. Points and condensers were used on 2-cycle bikes, too, and they have very high RPM limits vs. most car engines.

 

[The Chairman]

Yeah, that might make the spark last longer, but I'm not sure that's meaningful in the grand scheme of things.

When coils were ostensibly weak, duration was a very real factor. We only had a couple of KVs to work with, not over a hundred as we have today. Remove the condenser and quite often, the car would fail to run. I know, as I tried it. At higher RPMs, the engine would almost always miss. Old man Dahquevist, would often sabotage cars for me to figure out, often without telling me. No condensers were fun to figure out without removing the distributor cap.

 

[The Chairman]

There were *two* links there.

I found the second one.

The condenser absorbs the energy and prevents arcing between the points each time they open. This condenser also aids in the rapid collapse of the magnetic field.​

Yah, he needs to go back to school.

First off, a ballast resistor was used to reduce pitting, as well as to protect the coil in a key on/engine off situation by reducing current in the primary circuit. Most of us were resigned to replacing points every 6 to 12 months. The last sentence is bassackwards. A capacitor will never "aid in the rapid collapse". A quick tutorial in capacitors will back me up on that. Lastly, and back to the first statement, there's always arcing between points. Always. Condenser in or out of the circuit, and you'll always see the flash. Always. The author was pretty sloppy in that piece.

 

[The Chairman]

As a caveat, while I play with electronics a bit, I am not an electrical engineer!!! My knowledge comes from reading, experimenting, and also in the crucible of a little shop in Orlando Florida, where I started out sweeping the shop, and cleaning parts when I was 12, in 1969. I've pointed this out, but I've encountered many, many explanations of how points and condensers work. The one I've relied on was from a NASA engineer, who also taught me how and when to crimp. Could I be wrong? NO!!!, Ok, there's a small possibility that I'm wrong, but I've always approached issues with that kind of confidence. IOW, my concept has helped me to resolve hundreds of automotive issues regarding points and condensers. After all, the end game was a properly running car. Efficiency was always a thing, but the car needed to leave the shop, or you didn't get paid.

Funny story, in the early 70s, a chevy came into the shop not running. It was the first electronic ignition we had ever had to work on. Chester, the lead mechanic walked out to the car and peered under the hood. Suddenly, he exploded into a string of epithets and tossed the two wrenches he was carrying in the air shouting: "I'll have to become a %^*&@%$ TV repairman now!" After Chester walked away, Dahquevist handed me a cap and rotor and told me to slip them on. I tried the rotor first. Vrooooooom! I didn't know Chester could run! He was relieved and kinda pissed that the snotty nosed piss-ant kid pretending to be a mechanic fixed that car. Especially since I hardly ever touched domestic cars. A week or two passed, and one of our resident jokers hung a "We service TVs" sign above Chester's tool chest. No, not this exact one, but you get the idea.

 

[Gone for diving]

Poor Chester.
He would have a heart attack now.

 

[The Chairman]

Poor Chester.
He would have a heart attack now.

Indeed. Actually, that's what did him in, in the early 80s. I wonder if the first computer-controlled cars coming out in 1981 1/2 was a coincidence? Or was it 1980 1/2??? It was a Chrysler product, if I recall it rightly.

BTW, no one has answered one of my questions: which was the first emission control device?

 

[TrimixToo]

I found the second one.

The condenser absorbs the energy and prevents arcing between the points each time they open. This condenser also aids in the rapid collapse of the magnetic field.​

Yah, he needs to go back to school.

First off, a ballast resistor was used to reduce pitting, as well as to protect the coil in a key on/engine off situation by reducing current in the primary circuit. Most of us were resigned to replacing points every 6 to 12 months. The last sentence is bassackwards. A capacitor will never "aid in the rapid collapse". A quick tutorial in capacitors will back me up on that. Lastly, and back to the first statement, there's always arcing between points. Always. Condenser in or out of the circuit, and you'll always see the flash. Always. The author was pretty sloppy in that piece.

Gee, I always thought ballast resistors were there to assure a good spark with a weak battery when cranking while keeping the coil cooling after starting. On most cars, they were bypassed while starting.

 

[The Chairman]

Gee, I always thought ballast resistors were there to assure a good spark with a weak battery when cranking while keeping the coil cooling after starting. On most cars, they were bypassed while starting.

Only Chrysler bypassed the resistor during start up, if I remember correctly. They were used on both US and import models, but don't ask me which ones. Those were 60 years ago. Coils never ran hot, unless you left the key on, engine off. Kids would turn the car off and then back on to listen to the radio. Many would fry the coil if the points were closed. Even if they didn't fry the coil, they could fuse the points together. The smell of an overheated coil is simply horrible. Much worse than a ballast resistor on fluorescent lights. Thinking on it, I think you could buy coils that needed an external ballast, or those that had an internal one. It's been 60 years, after all, but controlling current was its job. I think I only had to replace one in all my 30-year career. I replaced far more coils and scads of points and condensers.

 

[The Chairman]

This is from Motortrend:

An ignition system with breaker points will surely suffer from reduced point life if the ballast resistor is removed, as higher amperage can damage the surface of the points causing failure. Additionally, if the ignition is left in the run position and the points happen to be open-or worse, barely open-electrical arcs can cause raised spots on the points resulting in a change in dwell timing or an engine that won't run at all.​

This actually talks about the key on engine off problem. https://www.motortrend.com/how-to/mopp-1110-ballast-resistor-guide-ballast-blast-off/