Just tried my '66 GTO's mechanical voltage regulator on my friend's '69 Firebird and it started charging his battery again. Even though he had bought a new voltage regulator a month or so ago. (And then an alternator.) His does not have the condenser installed on the voltage regulator like mine does, but there's a terminal for it.
I'm wondering if the condenser is necessary, maybe to keep the contacts from burning? I'd heard it was to prevent radio intereference, which we don't care about. I can't find anything in the service manual about it. If it's necessary to prevent contacts burning, maybe his new voltage regulator fried its contacts.
The condensor keeps the points from burning up. When the points break, for a short time, current keeps flowing in the condensor. So, the points don't arc. Then when the contacts close the condensor dumps it's charge across the closed points and is then ready to absorb the current from the next break.
I could be wrong, but I always thought they were for radio noise only since most don't have them. The points on the voltage regulator solenoids don't open and close at over 1000 times per minute like the igniton points (only when key is turned on/off), therefore they won't burnt out nearly as quick.
Radio static only.. nothing to do with the charging system, regulator or contacts inside.. If you don't have an AM radio in the car you don' t need it.
The points 'do' arc out and burn in those regulators or you wouldn't need new ones.... I was always under the impression you needed the condenser to slow this down.
Sometimes if they have arced while closed, you can thump on the regulator to get it going again if I remember right. The bad alternator might have caused this also. Some others you could open and inspect.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail > Just tried my '66 GTO's mechanical voltage regulator on my friend's
You're right, Mike. The condensor is there to stop RFI but it does it by stopping the sparking, which is an interrupted DC. Just like the condensor used to do on points, it provides a low impedance path for high frequency AC or interrupted DC.
While an electromechanical regulator might not be a critical to spark damage as ignition points were, the principle is similar.
Those points DO open and close thousands of times per minute. They are buzzing constantly, making and breaking contact and forming a (more or less) square-wave input to the alternator rotor. The induction of the rotor's coil smooths out the wave somewhat, but also causes sparking at the regulator points and they will ultimately either burn out or weld themselves shut. Filing them doesn't help much; they are silver-faced and once the silver is gone they quickly fail again. There is a resistor across the contact points. You'll find it under the regulator frame, in open air. When the points open, the current takes the path through the resistor, reducing the current flow to the rotor and thus reducing the alternator output voltage. If the voltage gets really high, the regulator's moving contact goes to ground and takes the rotor current to zero. The capacitor will reduce radio noise and contact point erosion, though many regulators will go for years without a capacitor. The rotor's induction isn't all that great and the resistor absorbs much of the peaking created by the rotor coil. After my students wire up the alternator charging systems on the teaching boards, we can see the constant, tiny spark between the points if the room is really dark. Those points are moving constantly. They have to, to keep the voltage exactly where the regulator wants it. The electronic regulator makes much more sense, modulating the current instead of repeatedly interrupting it altogether. I have schematics here of the electromechanical regulator. I can't find a similar one on the 'net.
To the OP.. you do NOT need this cap..... It is NOT a functional part of the charging system in any way... It is only a high frequency bypass to ground for radio noise suppression.
Its purpose and connection into the circuit in this application does not affect nor control the arcing at the voltage control contacts...
Having this cap in the circuit (or not) will not damage the regulator or affect the charging system in any way.
The capacitor on the GM Delco voltage regulator is ONLY for RFI suppression.. it is not in the "Field" circuit where the altenator field (rotor) contacts are located.
In the days of generator (as opposed to "alternator" charging systems, mis-connecting the RFI capacitor to the field terminal of the generator (an easy mistake to make in the day) would CAUSE a failure of the voltage control contacts in the regulator!! The cap in this particular application was mounted on the generator case, and designed to be connected to the generator "Armature" terminal which was in fact the current output terminal.
GM DELCO used to put a big round red cardboard warning tag on the "field" terminal of the generators telling you NOT to connect the capacitor wire to this (field) terminal! In this instance, the capacitor was being used to suppress the RFI from the arcing at the generator brushes which would be heard as a "whine" on an AM radio..
Of course these two connection terminals were located side by side on the generator case, and only a few of us could read the big red tag. So when this mistake was made the voltage regulator failure would occur within a couple hundred miles.
These uses are NOT related to the use of a capacitor in "Point + Condenser ignition system, where the cap serves an entirely different function in the creation of the High Voltage spark and in fact does absorb the arc at the contacts that is created by the collapse of the field in the primary of the ignition coil on the "break" of the contacts.
Again, I repeat, this capacitor on the Delco Altenator regulator base is NOT involved in the charging circuit in any way, and only exists to suppress the RFI generated by the arcing at the vr contacts... If you look at the back of the regulator base, you will see that the capacitor terminal is merely an extension of the "B" or Battery terminal lug. The capacitor from there to ground suppresses any HF RFI that might be generated from reaching the rest of the car's electrical system and thence being heard as a "popping" type of static on an AM radio..
Feel free to ask for more technical explanation an any time. School is out fo now .. there will be a quiz later
Both of the above. The regulator is switching an inductive load, which causes a huge voltage spike (and resulting arc) when you interrupt it by opening the contacts. The condensor damps out the voltage spike and prevents the arc. The arc is what causes radio interference.
I think we all agree that the capacitor is not functionally required for this circuit to function and the car to run.
It serves a purpose (else it would never have been put there) but the purpose is not a make or break situation (Well, I guess in one sense of the phrase, it is exactly there for 'make and break' situations;>)
Yes, I seem vaguely remember on a generator if you hooked a capacitor to the field circuit it would actually make the contacts buzz louder.
Hey Bob, Thanks for the info. Somewhere way back when, I think I used to know all that. But now I think i've reached the point where I've forgotten way more than I know.
You are correct. You beat me to it. Seems like there are a lot of people out there equating this condensor to condensor as in "points and condensor." WRONG!!
Just how does this condenser affect RF if it doesn't mellow out (buffer) the arc from the points?
If the points arced closed and stuck from a bad alternator, not having the condenser on the power feed might have allowed this to happen 'much' faster than if the buffer action from it was in there, or I am not remembering right.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
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It is more a matter of degree than the electronics behind it for the regulator. RFI suppression capacitors can be used at a lot of places where there is no functional or fundamental need for the.
The need for the capacitor is much more in a Kettering points setup, not so much for RFI protection but to lengthen the life of the points themselves. Left alone, the current through the points and the arcing due to this current can transfer metal from one face to the other causing early failure.
There's more to it than that. The arc that jumps the points as they open represents continued current flow, reducing the sharpness of the magnetic flux collapse that generates the spark voltage in the secondary. The condenser provides a temporary path for the electron flow as the points begin to open, and by the time the capacitor is full the points are too far apart to start any arcing, and the current stops much more abruptly. A bad (open) condenser will kill the engine just as quick as a shorted one. Just try starting the engine without the condenser installed; it won't run. Not enough spark. The automotive textbooks I've read have only the "points-burn prevention" theory as the reason for the condenser. Not until I studied for my aircraft maintenance engineer's ticket did I find the real reason for it in the aircraft texbooks. An old guy once told me many years ago that the (auto) engine wouldn't run without the condenser; he didn't know why, just that it wouldn't. I tried it, and sure enough, dead as a doornail. My Unison/Slick magneto manual says that the condenser also boosts the mag primary current for the next firing; this is true only because the magneto generates alternating current for the primary, as opposed to the DC system in the car.
That's an interesting way of putting it. The coil capacitor combination form a resonant circuit. When the points open the output is a very high voltage AC waveform if you don't have it hooked up to a spark plug. With a spark plug in the secondary circuit there is a discharge before the AC wave form reaches it's first peak. Before the points open the condenser is not in the current path. A capacitor will not pass DC current but does pass AC current.
That's right the condenser is designed (by design the correct size is picked to match the coil) to increase the voltage. The increased voltage actually increases the arcing at the points simply because more voltage means more arcing. There is another capacitor that is often placed on the positive terminal of the coil that is designed to reduce noise.
Kettering will work without a condensor.....for a short period of time. It has little to do with the series resonant circuit.
Kettering works by building an electromagnetic field in the coil during the 'make' or 'dwell' portion of the points. When you open the points, the field decays, and a high voltage is induced in the coil.
If you have a condensor which is badly out of range, or none at all, the points will be compromised.
If you have a shorted condensor, then you get nothing.
It will work at a much much lower voltage. The points themselves and the wiring have some capacitance but it needs more.
As I said remove the spark plug and you have a resonant circuit that will produce an AC waveform at the resonant frequency. Hook up an O-scope and try it if you don't believe me.
No they won't they will last forever because the engine won't run.
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