Ignition Coil Installation

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dodgedart1968

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Amston, CT
1968 Dodge Dart 225

I'm reinstalling my ignition coil. I didn't document the original arrangement when I disassembled this a year ago. Would someone please advise how the small can (condenser?) is connected. I assume its pigtail attaches to one of the coil terminals (+ or - ). My electrical diagram doesn't appear to show this part. Is this a radio suppression feature?

Thanks.

20220504_163023.jpg
 
Referencing my ‘72 Demon - pigtail attaches to
- terminal. It is for radio suppression. I believe yours should be the same.
Yote
 
Referencing my ‘72 Demon - pigtail attaches to
- terminal. It is for radio suppression. I believe yours should be the same.
Yote
Cap goes on PLUS (battery) side. Do NOT use one if you have a CDI/ MSD/ ignition
 
Oops- guess I shouldn’t rely on memory anymore.
Yote

When it comes to electrical/Electronic issues it would be difficult to get better advise than from 67Dart273.
 
Last edited:
I am trying to find a capacitor of that style for my 72 but cannot find one. Anyone have a lead on where to get them?
 
I am trying to find a capacitor of that style for my 72 but cannot find one. Anyone have a lead on where to get them?
Are you just looking for original mount style on capacitor or a original capacitor? I was also unable to find one but removed the mount from my old one and soldered it to a new one that had a removable slip in mount.
Yote
 
Are you just looking for original mount style on capacitor or a original capacitor? I was also unable to find one but removed the mount from my old one and soldered it to a new one that had a removable slip in mount.
Yote
That's a great idea! I'm looking for the original mount style. My old one will be usable!
 
I am trying to find a capacitor of that style for my 72 but cannot find one. Anyone have a lead on where to get them?
Most "traditional" ignition parts suppliers have universal ones. NAPA/ Echlin, etc. I think one was something like "RC-1" for "radio capacitor part no. 1"


And..........more.........dumbing down of 'Murica..........

https://www.napaonline.com/en/p/ECHRC1

It's not a "distributor capacitor............"

NAPA has gone full stupid......

Here's some more

https://www.napaonline.com/en/searc...and-condensers/alternator-condenser/201583916
 
from a deep article...or everything you always wanted to forget about condensors...
"The condenser must be of proper rating. If it is
either over or underspecced for the application, the points will pit and
burn. Remember the minus-minus-minus rule: If the minus (ground,
stationary) point is minus metal (pitted), then the condenser is minus
capacity (underspecced). The obverse applies, though it becomes the
"plus-minus-plus" rule: If the plus (positive, movable) point is minus
metal (pitted), then the condenser is plus capacity (overspecced).

That said, an engine will run OK with a fairly wide range of capacitance
in the ignition primary; years ago the condenser on my '65 Valiant failed
on my way to high school one morning. The engine hiccuped, coughed and
sputtered the remaining 1/4 mile; I coasted to a stop in a parking space.
No auto parts stores within convenient distance, but there was a hardware
store across the street. Come lunch hour, I went in and bought a small
condenser for a Tecumseh lawnmower engine. Wrapped a few turns of bare
wire around the condenser body and grounded the other end of that wire.
Put the condenser's lead wire on the coil negative. Car started and ran
fine and got me home, where I could install a correct condenser.
For the secondary effect of reducing AM radio noise
A different condenser -- the radio noise suppression condenser -- is used
for the bulk of this job. It is connected across coil + and ground. What
is commonly referred to as the "distributor condenser", i.e., the one that
permits the ignition system to function, is connected across coil - and
ground."

and "The condenser(capacitor) is about .22uf give or
take for design differences. I don't know what the mH rating of a coil
is, but the coil is a electrical device known as a auto-transformer.
It's like a regular transformer, but both the primary and secondary
share some of the windings.

The capacitor is wired in parallel to the points and in series to the
coil. The capacitor tries to maintain a constant voltage while the coil
tries to maintain a constant current. The basic design of a automotive
ignition circuit is basically a series resonance circuit not unlike
those used in radio.

When the points are closed, the capacitor is shorted out and current
flows from ground, through the points, through the coil, and out onto
the positive power rail. This sets up a magnetic field around the
windings of the coil. At the moment that a sparkplug is to fire, the
points open which interrupts the current flowing through the coil, but
the coil is charged (magentic field), and in an attempt to keep the
current going, the coil discharges right into the capacitor.

At this point, when the coil is fully discharged, there is a voltage
charge on the capacitor in the range of +700-1000 volts in reference to
ground. Since this is much higher than the +12V rail that the other end
of the coil is connected to, the current flows BACKWARDS from +12V,
through the coil, and into the capacitor to even the charge. Because
there is little resistance in the coil, a high amperage pulse is
generated through the coil primary, and with a winding ratio of 40:1,
causes a voltage spike between 28KV and 40KV on the secondary, which is
more than enough to jump the gap between the rotor and distributor cap,
and the gap on the plug itself.

A leaking capacitor will disapate some of the charge before it can be
used to draw the current through the coil resulting in a lowered high
voltage output and a weak, or no spark condition.

A shorted capacitor will cause a no-spark condition because the current
will still flow through the coil.

A open capacitor will burn the points because the points will be forced
to absorb the discharge from the coil causing them to arc, and you will
get a weak or no spark.

Too little capacitence will cause the points to burn do to the same
reason that a open capacitor will. But, it may or may not cause a
weak/no spark condition depending on how much under the spec the cap is.

Too much capacitence will cause a weak or no spark condition because the
voltage across the capacitor will not be high enough because of the
larger value. The bigger the cap is, the bigger the charge on the coil
has to be to get it to the 700-1000 volt range.
--
Daniel Rudy

Dont know who Dan Rudy is but he is pretty sharp on this subject.
 
The OP is talking about the condenser that mounts on the side of the coil for RF suppression, not the cond inside the dist for the points.
 
Some of that info in post #12 is wrong. There is nothing like 700-1000v of back EMF across the coil. More like 200-250v for inductive ign. It is that back EMF that generates the high sec voltage, according to the Turns Ratio of the coil. The MSD Blaster 2 coil has a 100:1 TR. It doesn't generate a sec voltage of 100,000v....
 
Most "traditional" ignition parts suppliers have universal ones. NAPA/ Echlin, etc. I think one was something like "RC-1" for "radio capacitor part no. 1"


And..........more.........dumbing down of 'Murica..........

https://www.napaonline.com/en/p/ECHRC1

It's not a "distributor capacitor............"

NAPA has gone full stupid......

Here's some more

https://www.napaonline.com/en/searc...and-condensers/alternator-condenser/201583916

I did pick one up from orielly. It just doesn’t have the same style mount. So, I’ll do what the OP suggests and move the bracket.


My mistake calling it a capacitor. I knew better
 
A short story about what that capacitor does. It provides a close AC path, to ground. Without it, path is back to battery +. That 3 to 4 foot path is a good antenna. In electronic circuits it would be called a bypass capacitor.
 
from a deep article...or everything you always wanted to forget about condensors...
"The condenser must be of proper rating. If it is
either over or underspecced for the application, the points will pit and
burn. Remember the minus-minus-minus rule: If the minus (ground,
stationary) point is minus metal (pitted), then the condenser is minus
capacity (underspecced). The obverse applies, though it becomes the
"plus-minus-plus" rule: If the plus (positive, movable) point is minus
metal (pitted), then the condenser is plus capacity (overspecced).

That said, an engine will run OK with a fairly wide range of capacitance
in the ignition primary; years ago the condenser on my '65 Valiant failed
on my way to high school one morning. The engine hiccuped, coughed and
sputtered the remaining 1/4 mile; I coasted to a stop in a parking space.
No auto parts stores within convenient distance, but there was a hardware
store across the street. Come lunch hour, I went in and bought a small
condenser for a Tecumseh lawnmower engine. Wrapped a few turns of bare
wire around the condenser body and grounded the other end of that wire.
Put the condenser's lead wire on the coil negative. Car started and ran
fine and got me home, where I could install a correct condenser.
For the secondary effect of reducing AM radio noise
A different condenser -- the radio noise suppression condenser -- is used
for the bulk of this job. It is connected across coil + and ground. What
is commonly referred to as the "distributor condenser", i.e., the one that
permits the ignition system to function, is connected across coil - and
ground."

and "The condenser(capacitor) is about .22uf give or
take for design differences. I don't know what the mH rating of a coil
is, but the coil is a electrical device known as a auto-transformer.
It's like a regular transformer, but both the primary and secondary
share some of the windings.

The capacitor is wired in parallel to the points and in series to the
coil. The capacitor tries to maintain a constant voltage while the coil
tries to maintain a constant current. The basic design of a automotive
ignition circuit is basically a series resonance circuit not unlike
those used in radio.

When the points are closed, the capacitor is shorted out and current
flows from ground, through the points, through the coil, and out onto
the positive power rail. This sets up a magnetic field around the
windings of the coil. At the moment that a sparkplug is to fire, the
points open which interrupts the current flowing through the coil, but
the coil is charged (magentic field), and in an attempt to keep the
current going, the coil discharges right into the capacitor.

At this point, when the coil is fully discharged, there is a voltage
charge on the capacitor in the range of +700-1000 volts in reference to
ground. Since this is much higher than the +12V rail that the other end
of the coil is connected to, the current flows BACKWARDS from +12V,
through the coil, and into the capacitor to even the charge. Because
there is little resistance in the coil, a high amperage pulse is
generated through the coil primary, and with a winding ratio of 40:1,
causes a voltage spike between 28KV and 40KV on the secondary, which is
more than enough to jump the gap between the rotor and distributor cap,
and the gap on the plug itself.

A leaking capacitor will disapate some of the charge before it can be
used to draw the current through the coil resulting in a lowered high
voltage output and a weak, or no spark condition.

A shorted capacitor will cause a no-spark condition because the current
will still flow through the coil.

A open capacitor will burn the points because the points will be forced
to absorb the discharge from the coil causing them to arc, and you will
get a weak or no spark.

Too little capacitence will cause the points to burn do to the same
reason that a open capacitor will. But, it may or may not cause a
weak/no spark condition depending on how much under the spec the cap is.

Too much capacitence will cause a weak or no spark condition because the
voltage across the capacitor will not be high enough because of the
larger value. The bigger the cap is, the bigger the charge on the coil
has to be to get it to the 700-1000 volt range.
--
Daniel Rudy

Dont know who Dan Rudy is but he is pretty sharp on this subject.
Wow, there's a lot to that. I always thought it just provided an alternate path to ground so the current didn't try to jump the point gap as they were opening. Thanks for sharing.
 
Another way of thinking about it: Points close and coil primary charges, when points open, coil discharges, coil + to battery completes circuit of electrical circuit. Inductance and resistance in wiring to coil, results in limitation. The capacitor firms up coil + voltage during transient spark event.
 
AND NOW another ANNOYING story from the old days.......

In the early 70's after getting out of the Navy after 6 years, I had a friend in my home town, Chev pickkup. He called me one late afternoon after work. "I'm trying to change the points in my truck, and I've checked and double checked and I CANNOT GET THEM TO RUN

So I go out there, and it's the typical '60's Chev V8--window distributor, adjustable points, allen wrench. I checked voltage, points resistance, dwell, even resorted to a feeler gauge, checked the dist for shaft play WTF. IT HAD BEEN RUNNING!!!

Turns out that "back then" GM and other aftermarket outfits had come out with a "uniset"---points and condenser in one unit. For some reason this minor point--which I'll explain--was lost on BOTH of us

He had bought a "standard" set of points, no uniset so no condenser. For some reason, I had not noticed THERE WAS NO condenser in the dist.

The thing that "fried our brains" is that his was an AFTERMARKET "uniset" and IT DID NOT HAVE a conventional condenser. Rather, it had a tiny little CERAMIC condenser/ capacitor, and otherwise looked like a "non" uniset!!! If either of us had noticed that there was NO CONDENSER in the distributor, it would have been an instant AWAKENING!! LOL

Below, an aftermarket / GM style uniset with "regular" condenser. This is NOT what came out of his distributor. By the way NEVER EVER buy or use P&D (Piddle and Diddle) breaker points!!!

I've never seen a photo of the type I described--nor do I know who made them

Chevrolet-Pontiac-Unipoints-Uniset-Ignition-POINTS-Contact-SET.jpg
 
Also, there is a LOT more to capacitors than many realize, and far above my knowledge. For example, high power linear RF amplifiers---------there is, has been, and may be many. All the way from "dirty" junk made by pirate CBers to decently designed legal amateur radio amplifiers, and on to really rugged commercial and military equipment.

In the output circuit you must have a cap that will withstand the very high anode voltage of the output tube(s) but at the same time conduct the AC waveform of the RF output in an efficient manner. THIS TASK CAN PROVE TO BE difficult, and depending on the impedances involved, even more so. Some caps can have many of the same "specs" on paper and yet not be able to carry the high RF current necessary for good operation.
 
The article Pishta posted mentioned "leakage." This is a BIG problem with igntiion condensers/ capacitors. Probably 70% or more of the old outboards I have been into have leaky capacitors. THERE IS ONLY ONE WAY to test for this and that is a leakage test involving HIGH VOLTAGE near the top of the operating voltage of the circuit and the rating of the cap. These magic little multimeters and testers you buy that you carry in your pocket do NOT do this.

By the way, in the outboards, I do not re-install original type caps. I buy "orange drop" poly caps and use those. They mostly "last forever" and are completely sealed against moisture
 
J_anderson, post #15. You didn't make a mistake. Condenser or capacitor, same thing in electrical theory. The term condenser seems to be used more often in the auto world & is probably an older term.
 
Also, there is a LOT more to capacitors than many realize, and far above my knowledge. For example, high power linear RF amplifiers---------there is, has been, and may be many. All the way from "dirty" junk made by pirate CBers to decently designed legal amateur radio amplifiers, and on to really rugged commercial and military equipment.

In the output circuit you must have a cap that will withstand the very high anode voltage of the output tube(s) but at the same time conduct the AC waveform of the RF output in an efficient manner. THIS TASK CAN PROVE TO BE difficult, and depending on the impedances involved, even more so. Some caps can have many of the same "specs" on paper and yet not be able to carry the high RF current necessary for good operation.
Sounds like you may be a "ham"!?
 
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