Bad Condenser Symptoms?

One more while I've got photo bucket working, just couldn't resist. This is my sept 29 that I've had since the spring of 1960. I must know something. I've been doing all of the work on mine since I was 13 years old. Now probably in my september days.
Sep.jpg
 
marc hildebrant said:
Group,

The capacitor (condenser) has to be installed close to the points to work properly.

If it's located away from the points, the inductance of the wire between the cap and points will work against the operation of the cap.

Marc
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Why would the wire mean anything being the back emf is coming from the coil it self, not the points? I would think, the closer to the coil the better?

I think the proof is in the pudding and it sounds like Purdy has not been burning points.


How long will it take to destroy points without a cap? As in, if you get stranded because the cap shorted can you just pull it out and run without it, or will you only make it a mile or 2 before the points are toast?
 
MrTube said:
. . . How long will it take to destroy points without a cap? As in, if you get stranded because the cap shorted can you just pull it out and run without it, or will you only make it a mile or 2 before the points are toast?
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You may not get a spark at all, or at best a very weak one. Without the cap to directly absorb the reverse EMF the waveform falls at a much shallower and irregular slope, as the electrons must wait their turn to arc across the points. If it does run, the points will be toast in about 20 minutes. I've seen this demo on a dizzy machine with a scope.

Unrelated subject- I'm clueless as to why only half of your monitor top valve seat corrodes. Turbulence erosion?
 
An open condenser ? Engine won't run. Unhook it and see if it'll run.
Length of condenser line/wire ? I don't think it much cares. Those little electrons can run faster than you think.
 
MikeK said:
You may not get a spark at all, or at best a very weak one. Without the cap to directly absorb the reverse EMF the waveform falls at a much shallower and irregular slope, as the electrons must wait their turn to arc across the points. If it does run, the points will be toast in about 20 minutes. I've seen this demo on a dizzy machine with a scope.

Unrelated subject- I'm clueless as to why only half of your monitor top valve seat corrodes. Turbulence erosion?
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Ah, that makes sense. So the cap is needed for the circuit to work properly as well as protect the points.

Unrelated - Not sure on the valve seat, I'm wondering if its flash gas which apparently is also a big problem in modern day units destroying TXVs. I'll probably never know why its happening but the cap tube will solve the problem anyway.
 
Patrick L. said:
An open condenser ? Engine won't run. Unhook it and see if it'll run.
Length of condenser line/wire ? I don't think it much cares. Those little electrons can run faster than you think.
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The inductance of a long wire to a remote cap. is the problem. That's one of the reasons why the cap is near the points.

Marc
 
I've had NO problems with a longer wire or connected directly to the coil. When I got my first model A some parts had been removed. It didn't run and there was no condenser.I was only a teenager. I didn't have the correct condenser and there was nowhere to mount a modern style condenser in the model A distributor. I removed the condenser from a fifties model chevy six cylinder and mounted it on the firewall. I cut the clip off the pig tail skinned the pigtail wire and twisted on a longer wire. I run this wire down to the distributor and connected it to the lower plate and it worked good, really. It was just common sense to me and I really had nothing to lose. I was later shown by an older guy how to connect the condenser directly to the coil. Both ways work good. Good modern condensers were available at parts houses in the day. the object was and is to get the condenser away from the heat of the exhaust manifold. Of course this ain't original but is a novelty to me.
 
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marc hildebrant said:
The inductance of a long wire to a remote cap. is the problem. That's one of the reasons why the cap is near the points.

Marc
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Patrick L. said:
Shhhh. Can't say that too loud. Can't allow the car to hear it. It might decide not to run. :)
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I still want to know why the points matter at all when it is the coil you are working with? The back emf is coming from the coil, not the points.

So doesn't it make more sense to have the cap by the coil? Shorter wires!
 
MrTube said:
I still want to know why the points matter at all when it is the coil you are working with? The back emf is coming from the coil, not the points.

So doesn't it make more sense to have the cap by the coil? Shorter wires!
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The points are only the switch. The condenser is actually what feeds the coil, so to speak, simply put. And yes, if you're worried about wire length then the closer to the coil, the better.
 
Patrick L. said:
The points are only the switch. The condenser is actually what feeds the coil, so to speak, simply put. And yes, if you're worried about wire length then the closer to the coil, the better.
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The battery feeds the coil, not the cap. The cap seems more like a shunt than anything.
 
Just spotted this conversation.

The coil stores, and releases the high voltage energy when the primary circuit is opened. When the primary circuit is opened by the points, there is a natural tendency of the points to spark. The condenser helps suppress that spark so it does not become so violent as to damage the points surfaces quickly.

Second (and most important), the condenser provides a ground for the bottom end of the coil secondary against which the coil works to produce the high voltage spark as the field collapses.
 
MrTube said:
The battery feeds the coil, not the cap. The cap seems more like a shunt than anything.
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Yes, and, no. Google is a wonderful thing. There is more reading there than one can handle. Of course, like a lot of things on the internet, some are wrong. But, they can be filtered out fairly quickly. Ignition systems are pretty simple, but, at the same time, complex.
Why a condenser is called a condenser is beyond me, its just the way things are. But, its function is pretty neat.
 
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