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Heres another one one external charging systems,

This was written by another member, a very good write up on how it works and how to troubleshoot a externally regulated charging system.
Peter F said:
I dug this out from before, hopefully it help. If not, just post or send me your questions.

I'll try to provide a simplified explanation of how the externally regulated alternator and regulator work here. This explanation starts from a parked car with engine off state.

The regulator brown #4 wire is connected through the light bulb to 12V whenever the key is in the ON position. The other end goes through a set of points in the regulator and then out the F terminal to the field winding in the alternator. So some current begins flowing in the field winding from this connection. The little bit of current flowing produces a weak magnet field in the alternator and also lights the bulb.

When you then start the car, the weak magnetic field from above begins rotating which makes the alternator producing a little bit of voltage. This voltage is fed from the alternator to the regulator on the white regulator #2 wire. This wire connects to a coil in the regulator and turns on a contact when the voltage goes above 3.2V.

Once the contact turns on in the regulator the #3 and #4 terminals are connected together. Terminal #3 is battery power so this puts battery power on both sides of the bulb and turns it off. This means the brown #4 wire should go to +12V. Also, this connects the field terminal right to battery power but still going through the points.

When the battery voltage goes above a set level, the F terminal is disconnected from the battery power by the points I kept mentioning. Then the voltage drops and the points close again. This on-off cycling happens rapidly and is how the voltage gets regulated.

From the above (KOEO = key on engine off and KOER = key on engine running).
F or #1 terminal (field) - KOEO = #4 slight voltage, KOER = 9-12V typically
#2 terminal (sense) - KOEO = 0V, KOER = >3.2V
#3 terminal (Battery) - KOEO = 12V, KOER = 12V
#4 terminal (light) - KOEO = F slight voltage, KOER = 12V

By 12V above I mean battery voltage, which may be 12V when engine is off but could be up to 14.5V when engine is running.

Check the light: Ground the brown #4 terminal wire at the regulator. When grounded the light should come on. If you don't have a light then skip this test. Test this with the connector off the regulator.

Checking the alternator: Jumper the blue wire F terminal to the battery post on the back. This should make it easily crank out 16+ volts. Next, connect a troublelight between the battery post and the F terminal. The light should come on and you should measure > 3.2V at the other alternator terminal. If it passes these tests, then it's in the regulator or wiring.

Checking the wiring: At the regulator connector jumper the brown light wire (#4) to the F terminal (#1) and you should be able to measure >3.2 volts on the other alternator terminal or terminal #2 of the regulator connector. If these tests pass, it is in your regulator.

When doing these tests, make sure you turn off or pull the fuses for any added electronics that you can. The alternator test can produce enough voltage to damage stuff.

Peter
 

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What does it mean when Peter has ">" in his writeup in post #2. Does this mean "and get"? Thanks!
 

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Let me preface this with the fact that I am an electrical novice. I just got my multi meter about 3 weeks ago.:D

I have a 69 camaro with the stock wiring with the external regulator. I am wondering if the voltage regulator is going bad and need to test it. I had some issues with the battery not charging (or shorting occasionally) and have done the following:

- Purchased new high amp alternator because I added electric accesories
- tested battery and it passed. Replaced it anyway as it was 6 years old and I suspected it may have an intermitant short.

The new battery voltage is 12.68 with the car off. It is only 13.4 with the car running at idle.

Voltage at the alternator (on the charge wire terminal) is 14.01

I did have some corrosian at the negative terminal on the battery which I read can be a regulator issue.

Any way, shouldn't I have more voltage than that at the battery and at the alternator? Can a bad regulator cause is the low voltage?

Thanks for the help.
 

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Yes, shouldn't be less than 0.4 volt loss measuring from BAT at alt to battery post itself.

The power lead from the alt goes to the fender harness and is crimped to the wire going from the horn relay to firewall connector, then to the horn relay buss bar, then onto the other attached red wire to the buss bar, then across rad support to a junction block, then to battery cable clamp.

Buss bar is very susceptible for corrosion - remove all and wire brush everything after disconnecting the battery, same with junction block.

With added electrical accessories, the best thing to do would be to remove the #10 AWG red wire and exchange it in its entirety with #8 AWG. Only problem is the firewall connector(s) and power lead to ignition switch & headlamp switch. Or branch out a separate terminal board just for power and wire extra accessories to it and a #8 supply wire to it.
 

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Thanks Everett. I guess my question is more about the voltage at the alternator itself. At that point, there is no loss at all caused by wire because I am taking the reading at the output post.

I thought the voltage at the alternator should be over 14.2 should it not?
 

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You're welcome. If still using a mechanical regulator, OE set-up, depends on how much is being asked for the alternator to supply, the internal setting of the voltage coil, speed of the alternator, and temperature of the battery electrolyte and regulator temperature.

There is an art, read procedure, to set the regulator. One has to let the alternator charge the battery back up after starting, 2500 RPM for 5 minutes, therefore the reason requesting temperature, the higher the temps, the less charging voltage needed to recharge. If voltage is low, then have to remove the reg cover, lengthen the spring to increase voltage, replace cover, and let the reg temperature stabilize again before voltage reading. Then, once set to a value, make a mental picture or take notes if the battery needs water, as in being cooked from over voltage, or needs to be externally charged as in under charging.

If you have no less than 13.2 volts at idle with headlamps on, and min 14 volts with engine at 2500 RPM and no accessories on, I'd say you're good to go. Fourteen-two would be nice, but you're gonna lose a couple tenths in the connections and wire temperature. I wouldn't worry about the 0.2 volts.
 

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Hi Guys, apologies if I'm not following protocols -- seems strange that I'm replying to a 10 year old thread, but I'm trying to get clarity on the troubleshooting guide above. I have a 68 with a powermaster externally regulated alternator. It is not charging the battery. I believe the wiring connections are good. Battery is fairly new & I keep it charged via a battery tender. Battery voltage typically measures 12.9 - 13.2 at posts, and drops to about 12.4 with engine running. Voltages at the charging post of the alt are nearly the same (12.9 engine off, 12.4 engine running) For the troubleshooting checks, I get:

F or #1 terminal (field) - KOEO = #4 slight voltage, KOER = 9-12V typically [6.4 v / 6.4 v]
#2 terminal (sense) - KOEO = 0V, KOER = >3.2V [0 v / 0 v]
#3 terminal (Battery) - KOEO = 12V, KOER = 12V [12+ v / 12_v]
#4 terminal (light) - KOEO = F slight voltage, KOER = 12V [6.4 v / 6.4 v]

I unplugged the voltage reg connector and jumped the F wire to the horn relay bus bar, which should put 12+ v in the field coils and produce max alt output -- if I understand the material above correctly. With engine running I still get about 12.4 v at the alt red wire post. I checked the alt ground & that seems ok.

This all seems to point to the alt as the problem. Can anyone help me with this? Thanks.
 

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To be perfectly honest I wouldn't even bother troubleshooting it unless its a concourse restoration and perfect car. Instead go buy a one wire alternator and ditch the old regulator and Alt.
 

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Alternator is at fault due to presented results from 'Full fielding' - battery voltage to field - as this action should have produced 36-40 VDC at BATT stud.
It would e nice if a vendor made an 'internal-regulated 10DN alternator, or provide the kit.
 

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A single wire alternator is fine if you are not trying to look original. I'm using the original alternator with a solid state external regulator. No regrets here.
 

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Yes, after reading various threads here, I just installed a solid state regulator (which btw didn't change anything). The alt is a chrome Powermaster unit which I bought about 3 years ago. Since my car is still in the mid-project stage, it isn't driven, only started/run in the garage periodically. Thus the alt has very little run time on it. So I don't really want to ditch the alt. I did take it apart and reclock it a while back and the brushes were sort of beat up in the process. I also remember the Batt post touching the ss sleeve on the fuel line for an instant and making a tiny spark. Not sure exactly when it quit producing voltage in all of this. I will play with it a bit more & try to troubleshoot.
 

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Oops, sorry for the delayed reply. Turns out the aftermarket replacement connector/pigtail that I had installed had the wire colors reversed compared to the stock harness. I finally figured this out after a lot of troubleshooting. Alt works fine now. Yet one more aftermarket part fiasco.
 
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