48 coupe- lets talk ignition condenser function

[Bolts]

I searched previous posts for condenser function and didn't get very far. Being a dummy about all this, I would like to learn enough to become an educated dummy on the condenser function.
I've always wondered what the capacitor does. I don't know very much about electronic theory beyond ohms law, so could one of you electrical types be so kind as to explain what it's purpose and function are?
Gracias.

[Terry,OH]

http://www.fas.harvard.edu/~scphys/c...E1b/E1b_3b.pdf This should help. Take it slow.

[Bolts]

Thanks Terry. OK. If I am understanding, the value of the capacitor is chosen to bring the operation of the transformer close to resonance for minimal power loss between the primary and secondary windings. That's one purpose, another being to short the voltage spike away from the point contacts to prevent burning.
So can we say a car might actually run without a condenser or possibly with a leaky condenser considering it may run bad due to low coil output and eventually quit due to point arching?

[Mr 42]

The Coil is an electric "gearbox".
The primary circuit where the points are in, create a magnetic field when the points are closed. Regardless how strong the magnetic field is nothing happens, so far.
Until the point's opens and the magnetic field collapses since the magnetic field moves thru the secondary windings it generates voltage in the secondary circuit. And since it has many more turns than the primary the voltage is higher, creating he spark over the sparkplug.
The thing is if you open the points without the capacitor there will be a small spark there to, eating up the points
The capacitor prevents that when it's loading up, and its also speed up the time for the magnetic field to collapse, the faster the higher voltage.

Edit: Took me some time to type this :-) You right it could work without a capacitor. But with the "tuned" setup when the capacitor give up the spark will go yellow caused by to low voltage. First thing you should check when you have ignition problems.

[bbrocksr]

May not start due to low coil output.
Bill

[Bolts]

Sponsored Links (Register now to hide all advertisements)

Mr42, Did you say when a condenser is bad the color of the high voltage spark will be yellow instead of blue?

Another thing. As a kid working in a gas station and also with my own cars, I saw many burned points. The cars were running. Is this condition just a normal wear characteristic on the points due to "imperfect" matches with the circuit components say from associated value tolerances, and so forth?
In other words if there is evidence of burning should the coil and condenser be replaced?

[Mr 42]

Yes when the condenser gives up, the spark will go yellow.
There will always be some spark going on since they only can tuning to a specific RPM range.

Here is some moving pics showing capacitor problems with magnetos.
http://brightsparkmagnetos.com/faqs/...ill%20work.htm

The explain the function really good her to.
http://brightsparkmagnetos.com/faqs/...%20magneto.htm

[rotorwrench]

The best way I could ever describe a capacitor is by comparing it to a hydraulic accumulator. The hydraulic accumulator has a diaphragm inside a containment vessel with a spring on one side to allow system pressure to push the diaphragm against the spring pressure and accumulate a charge of pressure inside the vessel. It can be set up to hold the system pressure after the pump is shut down which will delay the collapse of pressure long enough to do a little more work with the system after shut down. How much of a delay that is, depends on how big a volume the vessel of the accumulator is and how much pressure is stored in the spring.

A condenser works in similar fashion except we are dealing with electromotive force (voltage) instead of fluid pressure but the theory is nearly the same. The electromotive force pressure is strong enough to push the stored charge directly back through the primary as the magnetic field collapses. That delayed surge makes the collapse last a bit longer and gives a stronger inductive force through the coil core and into the secondary winding. It makes the spark last longer and therefore a better quality spark with the added effect of preventing arcing of the breaker points.

If anyone ever hands you a fully charged capacitor then you will feel how much voltage it has stored up. I had this trick pulled on me when I was a kid but it helped me see the light in more ways than one. Maybe some stars there too.

[66miles]

Apologies in advance for jumping in Bolts. But this might help you also. Having talked about the function of the condenser (capacitor), how would one go about testing one? Short of installing a new one a doing a comparison.

[rotorwrench]

Back in the day a person could find a capacitor tester pretty easy but not so much now days. The capacity has to be checked and it also has to be checked for leakage. Capacitors are rated in the farad but the little condenseres are in the milli farad range which is 1 thousandth of 1 farad. The flatheads used a condenser in the .21 to .25 mfd range.

It may be more practical to just buy several new ones and see which one works the best. If a person has a distributor machine like Bubba with an oscilloscope, they can be tested for function that way. I think Bubba has his own capacitor checker too but the average Joe doesn't.

[66miles]

Thanks for those numbers anyway rotorwrench. Knowing those at least a guy could go to a DECENT motor shop a specify a certain condensor range. I have a feeling that those things are pretty cheap! I'll but out again. Over to you Bolts.

[Bolts]

Originally Posted by 66miles

Thanks for those numbers anyway rotorwrench. Knowing those at least a guy could go to a DECENT motor shop a specify a certain condensor range. I have a feeling that those things are pretty cheap! I'll but out again. Over to you Bolts.

Check out the info from MR42 (thanks for that) showing the results of detuning the network by just changing the placement of the capacitor.
One important thing I learn from this thread is if you're having problems with a weak spark, check the points as a first step, if they're burned, the capacitor is probably the culprit which didn't prevent the points from burning. Then go from there.