Capacitor/condensor

[John Pasinski]

The assembly manual shows a capacitor (condensor?) on the voltage regulator as well as the ignition coil.
Does anyone know if these are still being sold, and what would the microfarad capacity be?
I'm assuming the coil capacitor is for static voltage to eliminate radio interference. Would they be similar to the distributor condensor?

[Steeveedee]

You can buy that at almost any auto parts store. They have different capacitance depending on the application, so the one on the voltage regulator is probably different from the one on the coil. It is indeed a "capacitor", per se, but is also called a condenser. I don't know where that terminology started. Probably something like catalytic "converter". In the chemical engineering and chemistry books, they are called catalytic "reactors", but people freak and think it is nuclear (NOT, it is chemical), so the word got substituted.

And yes, they are used as high-pass filters, conducting all the spark gap RF emissions (voltage regulator points opening and closing, fairly slow, ignition point opening and closing, a lot faster), which are high frequency, to ground, but do not pass DC power to ground.

[John Pasinski]

Originally Posted by Steeveedee

You can buy that at almost any auto parts store. They have different capacitance depending on the application, so the one on the voltage regulator is probably different from the one on the coil. It is indeed a "capacitor", per se, but is also called a condenser. I don't know where that terminology started. Probably something like catalytic "converter". In the chemical engineering and chemistry books, they are called catalytic "reactors", but people freak and think it is nuclear (NOT, it is chemical), so the word got substituted.

And yes, they are used as high-pass filters, conducting all the spark gap RF emissions (voltage regulator points opening and closing, fairly slow, ignition point opening and closing, a lot faster), which are high frequency, to ground, but do not pass DC power to ground.

Thank you Steeveedee.........I never knew there was supposed to be a capacitor on the coil. Makes much more sense knowing this especially with RF interference. Like our bodies, engines too run much better when all the filters are working.

[franken]

The one on the ignition coil is to reduce arcing at the point contacts. This is so reduce wear or erosion of the contacts, making them last longer.
I'd say the same is true at the voltage regulator.
For radio noise suppression they had resistor plug wires and plugs.
Since an inductive load (think magnetic field) resists a change in current, they tend to arc at contacts as they open. A cap absorbs and stores that energy, releasing it when the contacts close.

[Already Gone]

New question on old thread. I replalced my points distributor with a Pertonix Distributor and one of their coils and used their 7mm plug wires.. I also had my original alternator rebuilt and upgraded from a 37 amp to 55amp. Now I am now changing my original voltage regulator and it has the capacitor/condenser attached to it. My question is do I need to replace the capacitor/condenser when installing the new voltage regulator or do I need it at all.?

[Steeveedee]

Take a look at the points in your old voltage regulator. If one side has a "hill" and the other side has a "crater", your capacitor is bad- or at least, the wrong capacity. You definitely need a capacitor there to suppress the white noise that is generated when the voltage regulator points open and close.

[Already Gone]

Originally Posted by Steeveedee

Take a look at the points in your old voltage regulator. If one side has a "hill" and the other side has a "crater", your capacitor is bad- or at least, the wrong capacity. You definitely need a capacitor there to suppress the white noise that is generated when the voltage regulator points open and close.

But the new regulator doesnt have points.

[Steeveedee]

Originally Posted by Already Gone

But the new regulator doesnt have points.

Looking at Page 6Y-9 (page 401 of the .pdf) of the CSM, the transistorized voltage regulator appears to have internal capacitors C1 and C2. I don't see where the points style voltage regulator has a capacitor attached, though we know that it has an external capacitor. So, I really don't know, except that a transistorized system doesn't switch (make/break) like points, so you probably don't need the capacitor. I guess it really depends on what's inside your new regulator.

[mike16]

these images come from the assembly manual and other sources. If I recall correctly ther is another one attached to the back of the alternator.

[RichardJ]

You won't find these two capacitors if the vehicle had "Radio Delete" on the original options list. In 50 years, people do add things.
The coil-side and the regulator capacitor would both be 0.5 Mfd, but different wire end connectors give them different part numbers. Ignition points condenser is around 0.2 Mfd (Micro Farads).

>>But the new regulator doesnt have points.<<

Not necessarily true. If you go buy a new one, you will find most retailers offering two different ones that look nearly the same. The original regulators had two relays inside them. You can now buy solid-state regulators that are cheaper, do not have the two wire resistors on the bottom, weight less than half the original and have no relays inside.

The condenser isn't needed if the new regulator is solid-state, but the provisions are there for it so I'd use it.





>>Take a look at the points in your old voltage regulator. If one side has a "hill" and the other side has a "crater", your capacitor is bad- or <<

The condenser, missing or not, will have no effect on the life of the contact points in the old relay style regulator.
You may need to read up on Induction Ignition Systems. Ignition points do not burn because there is 12 volts arcing across them. Ignition points burn because there is 350-400 volts arcing across them. Or, I should say, trying to arc across the points. The condensers job is partly to try and suck up as much of that 350 volts as it can to keep the points from burning.

[franken]

Originally Posted by RichardJ

You won't find these two capacitors if the vehicle had "Radio
You may need to read up on Induction Ignition Systems. Ignition points do not burn because there is 12 volts arcing across them. Ignition points burn because there is 350-400 volts arcing across them. Or, I should say, trying to arc across the points. The condensers job is partly to try and suck up as much of that 350 volts as it can to keep the points from burning.

It's 12V on the low side not hundreds of volts, and on the high (plug) side it's thousands of volts. Let's try to keep the mythology out of things. Anyone can take a voltmeter and measure the low side voltage.

[Already Gone]

Originally Posted by RichardJ

You won't find these two capacitors if the vehicle had "Radio Delete" on the original options list. In 50 years, people do add things.
The coil-side and the regulator capacitor would both be 0.5 Mfd, but different wire end connectors give them different part numbers. Ignition points condenser is around 0.2 Mfd (Micro Farads).

>>But the new regulator doesnt have points.<<

Not necessarily true. If you go buy a new one, you will find most retailers offering two different ones that look nearly the same. The original regulators had two relays inside them. You can now buy solid-state regulators that are cheaper, do not have the two wire resistors on the bottom, weight less than half the original and have no relays inside.

The condenser isn't needed if the new regulator is solid-state, but the provisions are there for it so I'd use it.





>>Take a look at the points in your old voltage regulator. If one side has a "hill" and the other side has a "crater", your capacitor is bad- or <<

The condenser, missing or not, will have no effect on the life of the contact points in the old relay style regulator.
You may need to read up on Induction Ignition Systems. Ignition points do not burn because there is 12 volts arcing across them. Ignition points burn because there is 350-400 volts arcing across them. Or, I should say, trying to arc across the points. The condensers job is partly to try and suck up as much of that 350 volts as it can to keep the points from burning.

My old one which is original to the truck looks like the bottom one and my new one looks lke the top one. I checked the points on the old regulator and they are even, no hills or valleys. The cap was riveted on the new one so I drilled it out and put the cap from the original on it. I will put the original capacitor/condenser on the new one too so it looks original.

[RichardJ]

You want to measure voltage? Sure.

An oscilloscope measures voltage over a period of time. This is the primary voltage waveform over a 10 Millisecond period of time. Time varies with rpm.
Voltage is shown on the left hand vertical scale.

Starting on the left at the -5 millisecond mark, the voltage is just above the 0 or at the 12 V.
Voltage stays at 12 V for 2 ms or until the timeline reaches x, the vertical dash line. Here the points close, shorting the 12V to ground and now showing 0.0 volts.
When the points open, at the 0 millisecond point on the timeline, you see the voltage spike at about 325 volts.

You can't see this with a volt meter, but this is what the primary voltage actually looks like.