 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / February 2007what's the condenser for on a mechanical voltage regulator?
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. > Just tried my '66 GTO's mechanical voltage regulator on my friend's > '69 Firebird and it started charging his battery again. Even though [quoted text clipped - 7 lines] > 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. Ted On Feb 18, 8:02�pm, hil...@emailaccount.com wrote: > Just tried my '66 GTO's mechanical voltage regulator on my friend's > '69 Firebird and it started charging his battery again. Even though [quoted text clipped - 7 lines] > the service manual about it. If it's necessary to prevent contacts > burning, maybe his new voltage regulator fried its contacts. 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. Hank > 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 [quoted text clipped - 3 lines] > > Hank 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. Dan > On Feb 18, 8:02�pm, hil...@emailaccount.com wrote: > [quoted text clipped - 15 lines] > igniton points (only when key is turned on/off), therefore they won't > burnt out nearly as quick. Actually, at least one pair of contacts in a voltage regulator DOES open/close very fast. Maybe even faster than the engine points. > Just tried my '66 GTO's mechanical voltage regulator on my friend's > '69 Firebird and it started charging his battery again. Even though [quoted text clipped - 7 lines] > the service manual about it. If it's necessary to prevent contacts > burning, maybe his new voltage regulator fried its contacts. I think the main purpose of the condenser was to reduce static on the radio. Particularly on AM radio. -jim >Just tried my '66 GTO's mechanical voltage regulator on my friend's >'69 Firebird and it started charging his battery again. Even though [quoted text clipped - 7 lines] >the service manual about it. If it's necessary to prevent contacts >burning, maybe his new voltage regulator fried its contacts. 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. Bob 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 in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Just tried my '66 GTO's mechanical voltage regulator on my friend's > '69 Firebird and it started charging his battery again. Even though [quoted text clipped - 7 lines] > the service manual about it. If it's necessary to prevent contacts > burning, maybe his new voltage regulator fried its contacts. > 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. 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. >> 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 [quoted text clipped - 7 lines] >While an electromechanical regulator might not be a critical to spark damage >as ignition points were, the principle is similar. 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. <BG> 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 <G> Bob F. > >> 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 [quoted text clipped - 9 lines] > > > To the OP.. you do NOT need this cap..... 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;>) > >> 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 [quoted text clipped - 27 lines] > generator (an easy mistake to make in the day) would CAUSE a failure > of the voltage control contacts in the regulator!! 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. > The cap in this particular application was mounted on the generator > case, and designed to be connected to the generator "Armature" [quoted text clipped - 31 lines] > Feel free to ask for more technical explanation an any time. > School is out fo now .. there will be a quiz later <G> 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. -jim >>> 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 [quoted text clipped - 64 lines] > >Bob F. 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!! Don www.donsautomotive.com >>>> 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 [quoted text clipped - 21 lines] >> suppression.. it is not in the "Field" circuit where the altenator >> field (rotor) contacts are located. <snip unrelated rambling> >> 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 [quoted text clipped - 17 lines] > Don > www.donsautomotive.com Ok, so now you have me curious. 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 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Ok, so now you have me curious. > > Just how does this condenser affect RF if it doesn't mellow out (buffer) > the arc from the points? It does. Yes, the charging circuit will WORK without the cap, but the contacts on the relay will erode much faster than when the cap is present. Lots of RFI is a sign that the points are arcing, eliminating or reducing the arcing will make the contact points last longer. No "ifs, ands, or buts." > 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!! > > Don > www.donsautomotive.com 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. > > 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 [quoted text clipped - 13 lines] > 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. Dan > There's more to it than that. The arc that jumps the points > as they open represents continued current flow, reducing the sharpness [quoted text clipped - 3 lines] > full the points are too far apart to start any arcing, and the current > stops much more abruptly. 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. >A bad (open) condenser will kill the engine > just as quick as a shorted one. [quoted text clipped - 6 lines] > run without the condenser; he didn't know why, just that it wouldn't. > I tried it, and sure enough, dead as a doornail. 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. -jim > 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. > > Dan 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. > Kettering will work without a condensor.....for a short period of time. It will work at a much much lower voltage. The points themselves and the wiring have some capacitance but it needs more. > It > has little to do with the series > resonant circuit. 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. > Kettering works by building an electromagnetic field in the coil during the > 'make' or 'dwell' portion [quoted text clipped - 3 lines] > If you have a condensor which is badly out of range, or none at all, the > points will be compromised. No they won't they will last forever because the engine won't run. -jim > If you have a shorted condensor, then you get nothing. > > Kettering will work without a condensor.....for a short period of time. > > It will work at a much much lower voltage. The points themselves and the > wiring have some capacitance but it needs more. It works at a lower voltage because the inductive field has to collapse very quickly to give highest voltage. It cannot do that if the points are sparking. > 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. I am well aware that you will get a ringing waveform when the field collapses. > No they won't they will last forever because the engine won't run. I have never tried it, actually, but concede that if it should start at all, it wouldnt run for long. Have you actually ever tried this? On Feb 21, 7:03 am, <H...@nospam.nix> wrote: > > H...@nospam.nix wrote: > [quoted text clipped - 18 lines] > I have never tried it, actually, but concede that if it should start at all, > it wouldnt run for long. Have you actually ever tried this? I did. It won't run. Dan > > 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. > > I am well aware that you will get a ringing waveform when the field > collapses. Not usually. If there is a spark plug that fires the wave form gets arrested before it reaches maximum on it first peak. Only if there is no diversion of the current (by arcing in the secondary) will there be the damped sinusoidal waveform. > > No they won't they will last forever because the engine won't run. > > I have never tried it, actually, but concede that if it should start at all, > it wouldnt run for long. Have you actually ever tried this? Oh sure I have. Remember the type of points that had a condenser wire that just slipped in behind the points spring. After installing new points I once put the distributor cap and pinched the condenser wire between the cap and distributor. The engine started up and idled fine, but as soon as it was revved up the engine stalled and would not restart. When I open the distributor I found that as soon as the vacuum advance kicked in it pulled the condenser wire out of the circuit and the engine killed. After inserting the condenser wire back where it belonged and carefully routing the wire so that the cap didn't pinch it again the engine started and ran fine. With out the condenser hooked up it had a little spark, but the spark was very weak. Now I'll admit that the weak spark (low voltage) does have something to do with arcing at the points and you could probably design a set up that got a higher voltage with a different type point and coil configuration. So it may be possible to construct a point set up that worked without a condenser and that set up would probably not last as long. But that has to do with efficiency. The capacitor is sized so that it works efficiently. That is it produces the required high voltage with a minimum amount of current flow. A system without the condenser would require alot more current flow thru the coil to generate the same high voltage output, and thus the points and coil would not last as long. -jim > With out the condenser hooked up > it had a little spark, but the spark was very weak. I showed this same thing in a different way trying to test the coil on my Sportster motorcycle. Used a plain piece of wire instead of points and condenser, touching the wire to ground manually and pulling it off to create the spark, seen by looking at a spark plug out in the open (grounded to the threads, of course). The spark generated in this manner was so puny it was hardly visible. When I added a condenser the spark was big and audible. In article <1172078658.252535.102630@q2g2000cwa.googlegroups.com>, > > With out the condenser hooked up > > it had a little spark, but the spark was very weak. [quoted text clipped - 6 lines] > manner was so puny it was hardly visible. When I added a condenser > the spark was big and audible. Try he same thing but do the make/break by scratching the wire across a file. Plenty hot spark... Then again, Chrysler service manuals in the late 70s early 80s showed how to rig up a coil tester that used a condenser in parallel with the make/break wire. > Just tried my '66 GTO's mechanical voltage regulator on my friend's > '69 Firebird and it started charging his battery again. Even though [quoted text clipped - 5 lines] > contacts from burning? I'd heard it was to prevent radio > intereference, which we don't care about. 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. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.