Reference: Ignition condensers

[Mike Kelly]

Modern ignition condensers are CRAP read this:


[QUOTE][QUOTE]By Steve Maas, Long Beach, California.

The Problem


Because of repeated reports of failures of ignition capacitors (the modern name for condensers)
I decided to investigate the cause by dissecting some failed units. I examined three capacitors, two failed ones(Nos. 1 & 2) and a third, unused one, (No. 3) as a
control. Nos. 1 and 2 were distinctly different apparently from different manufacturers. No. 3was marked "Made in England," so it could have been a Lucas product. Electrical Tests First, I tested all three for open or short circuits. They all were OK. Next I checked the capacitance, and all seemed OK in this respect, too, with capacitances between 0.20 and 0.22 microfarads (the spec is0.18 to 0.25). Surprisingly, the "failed" units seemed to be working! I also checked for insulation breakdown. Since the ignition system subjects them to about 250volts, peak, it seemed possible that the high voltage might have blown a hole in the insulation. I tested them at 175V; all were OK at this level. Physical Examination Next I disassembled them, looking for a sign of failure, such as arcing across the capacitor or through the dielectric.

Starting with no. 1, I ground off the edge of the case so it could come apart. Inside was a capsule (the capacitor itself) and a corrugated nickel-plated contact. The other contact was a brass washer to which the wire was soldered.
The capsule consists of two layers of foil with a thin mylar insulating layer between the metal layers. It's all rolled up into a cylinder with one metal layer sticking out one end and the other layer sticking out the other end. Electrical
contact is made to the ends by simply squashing it all together. The capsule was smaller than the can in which it was mounted, so it conceivably could wiggle around a bit in response to shock and vibration. Not good.
This is a stunningly cheap, unreliable design. There is nothing to keep a consistent force on the capsule contacts; without that, there is no guarantee that the electrical contacts remain good, especially if the mylar expands and
contracts with temperature changes. There should some kin There should some kind of spring to keep the pressure on the contacts, but there is nothing even the least bit springy. The lack of any support for the capsule is also troubling, as it
could move around if it doesn't fit tightly. That would also affect the electrical contacts. This is all especially important, since the capacitor carries a surprisingly high current. I estimate it at about 2.5 amps, peak. This means
that even a small additional resistance is likely to affect the ignition pulse and waveform, with serious effects on the operation of the car. I started by unwrapping the capsule but found no
signs of insulation breakdown. I then looked into the can and examined the corrugated washer; there I saw clear indications of arcing at the contact points between the washer and the can. This is shown in the second picture below.
Although it's hard to see in the photo, especially inside the can, it is quite clear in real life.


No. 3, the presumed Lucas capacitor, was a little better quality, but not much. There were no marks inside it since it was unused. It had no corrugated washer, so the can-end electrical contact was simply to the body of the can.
The other contact was a brass piece that was crimped to the wire instead of being soldered. Again, the whole thing was simply squashed together with no spring of any kind to keep the pressure on the capsule. The capsule was also
considerably smaller than the inside of the can, allowing it to move around quite a bit. Any such motion is likely to damage the electrical contact. The design of no. 2 was very similar to no. 3. It showed clear indications of significant arcing at
the can end. Not only were there marks on the can, but there were marks on the capsule as well. It clearly had arced quite a bit. Conclusion It appears that these capacitors are failing because of poor design and equally poor
manufacturing quality, resulting in an erratic electrical contact at the can end of the mylar/foil capsule. Since there is nothing to maintain pressure on the capsule, temperature variations and vibration eventually cause this contact to
loosen, and the can end begins to arc. even cause an intermittent open circuit in the capacitor, which in turn results in a weak spark, burned points, and rapid ignition failure. It is also consistent with reports that new capacitors
often seem to work well for a short period of time and then fail. What to Do About It? The poor quality of these components is more than a little disturbing. The chance of one failing, sooner or later, is pretty high. Such
sloppy manufacturing and design quality really should not be tolerated in cars that have enough potential reliability problems already. The solution, of course, is to find an accept able replacement capacitor. One good option is a commercially available capacitor called a "snubber" capacitor. These are designed for soaking up large voltage spikes in power electronic components, much like what the capacitor in an automotive ignition system should
do. They are not cheap by capacitor standards, a few USD, but not expensive by automotive standards. An Alternative Capacitor I found (in the USA) a good replacement capacitor for the unreliable ones that are
currently being sold by the usual suspects. (Ed: Australian readers might try a Google search on’ snubber capacitor’ for more technical information and sources. Look for a capacitor value of about0.22µF (0.22 microfarad) and a voltage rating of
600V or higher).

There are many that should work; the one I bought is overkill, for sure, but still is less than$US3. And it should last forever; no need to replace it periodically. Photo 5 shows the snubber capacitor I bought. It is a little large, about 1.25" x 1" x 0.5", and definitely won't fit inside most distributors. I mounted the capacitor on a piece of printed circuit board(Photo 6) so it could be mounted righto n the coil. This is a little clumsy, and ; for many of you that matters, so
maybe a little more thinking about mounting the capacitor is in order.[/

[Jordan Baker]

I’ve had very good results with the modern items I talked about in this thread.

http://www.mapleleafup.net/forums/sh...ight=Condenser

[Mike Kelly]

I’ve had very good results with the modern items I talked about in this thread.

http://www.mapleleafup.net/forums/sh...ight=Condenser
__________________

Yep, this article I found is basically the same solution:


There have been many many problems here in Aust. with vintage cars and the poor quality replacement ignition capacitors. It has been a ongoing issue with older car owners here. Don't know about other countries.

Here are the pics for the article... I will try and improve the txt spacing .