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Old 09-18-2020, 01:14 PM   #8
Kevin in NJ
Senior Member
 
Join Date: May 2010
Location: South East NJ
Posts: 3,398
Default Re: Dual Condensers?

As an electrical engineer lets talk about capacitors.

Putting 2 capacitors in parallel will add the values of the capacitance. So you would go from .22 to .44mfd. That means it will absorb more energy. Potentially an energy loss for the coil.

Capacitors are just 2 parallel conductive plates with a separator. They only conduct electricity when the voltage is different between the sides (under ideal conditions).
BUT as they fail they allow for current to flow but a tester will show that the capacitance is still proper.

Usually the voltage for a capacitor is much higher then needed. For the ignition circuit it is up around 450volts. You can actually see some pretty high voltage for very brief periods of time but with very little current. So 6 or 12 volts is not a factor.

The purpose of the capacitor is to limit the arcing on the points. So it absorbs some of what is called back EMF from the coil. If too much current is allowed to flow then you lose some of the energy going to the spark plugs. There is a balance. You need the capacitor at the points or as close as possible because that short bit of wire is a resister. At the quick current levels seen the small resistance will increase the voltage at the points. More voltage means the electricity can jump a larger gap. The major fail point for the type of capacitor used on a car is heat. So clearly getting the capacitor out of the heat would be great. But then it could not do its job as it MUST be as CLOSE as possible to the points.

Modern points are not the answer. The problem is today the points you buy for the modern cars are all done low bid in China. You get luck of the draw. Go read up on Mustang forums and you will find people complaining about failures out of the box and after short use for even the name brand like Motorcraft. At work I buy some expensive computer motherboards because they use high reliablity capacitors. The reason why all my old motherboards have failed, the capacitors go bad. Now I can not complain as these were high end computers and we got 8 to 12 years of 24/7 use.

For all Model A cases I will say you are best to use the burnout proof condensers from a known company. A&L I know makes good ones, or at least used to.

For the people that put he condenser at the coil and the dist. Well they likely are just cutting down on the spark at the plugs. But the wire between is a resistance and it creates what is called a tuned circuit low pass filter of some sort. It could cause the spark to vary depending on rpm or make the dist condenser need to absorb more energy then it was intended.

The radio suppression capacitors would be of a different value. Likely a factor of ten lower in the .02 range as you are trying to clear out a much higher frequency noise. But I could be wrong here, I did not find anything referencing what was used in the later cars. You also have to consider later cars were much different. There would be a resistor or resistor wire in the coil circuit.

What to take away from this:

You can not tell if a condenser is bad without a coil condenser tester or a special condenser tester. A meter just tells you what the capacitance of the device is and a failed unit can still show the correct capacitance (my experience is most will).

Modern built V8 condensers can and will still fail even out of the box. A burnout proof unit is often made from better quality capacitors so they will just work for a long time.

The condenser MUST be as close to the points as possible.

One correctly sized condenser is all you want.

I have intentionally kept the text simple above so hopefully you can understand what I have said.
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