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> Alternator question., Not Charging.
Spoke
post Sep 10 2019, 08:47 PM
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QUOTE(Gatornapper @ Sep 10 2019, 09:52 PM) *

Mark -

The first comforting thing I've heard about that jumper - as the Porsche dealer did the carb conversion, the jumper definitely doesn't look like a shade-tree mechanic one, but a very professional one....


The jumper is well done and quite unique. The jumper on your 914 definitely stumped the band although it does work. SirAndy's solution is the one you want.

Put it on your list of things to correct. It is not as important as getting the alternator/VR working.
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GregAmy
post Sep 11 2019, 05:28 AM
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QUOTE(Gatornapper @ Sep 10 2019, 09:22 PM) *
Funny that while I rev the engine up and down, the GEN light goes from Dim/off at idle to bright a 2,000 rpm - while the battery voltage remains fairly constant at 12.2 +/-.

Post #23 (on page 2 of now 7):
QUOTE(GregAmy @ May 13 2018, 03:22 PM) *
...a slightly different problem: GEN light comes on strong with key on, engine not running, But then the GEN light glows very soft at idle, and then comes on stronger as RPMs build.

Post #36 (also on page 2 of now 7):
QUOTE(GregAmy @ Mar 25 2019, 09:58 PM) *

Quick follow up: alternator replacement solved it. I'm guessing a bad diode.

That's such a hateful job...

Replace the alternator.


Edit: print these out in color, and keep them in your manual. As an electrical professional, you can appreciate their value. I've got mine spliced together in a multi-fold so I can expand them out on the toolbox and work through any/all electrical issues...

http://web.archive.org/web/20140328013841/...al_diagrams.htm
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Gatornapper
post Sep 11 2019, 08:30 AM
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Thanks Greg....started doing so on many of the comments here many schematics from the start. Thanks also for the list at Pelican - I've got a lot of their diagrams, but not the list you sent.

Trying $200 Bosche VR and working relay board tonight/tomorrow. If they do not correct things, will rebuild alternator or have it rebuilt. Like you, I suspect they will change nothing.

If the alternator is bad, I want a technical explanation for why it passes all the tests except for the one that counts - working.

Just don't want to rebuild alternator and discover I still have the same problem......since no one can explain why I'm getting these results, I see that as a possibility - one I do not like at all.

GN

QUOTE(GregAmy @ Sep 11 2019, 05:28 AM) *

QUOTE(Gatornapper @ Sep 10 2019, 09:22 PM) *
Funny that while I rev the engine up and down, the GEN light goes from Dim/off at idle to bright a 2,000 rpm - while the battery voltage remains fairly constant at 12.2 +/-.

Post #23 (on page 2 of now 7):
QUOTE(GregAmy @ May 13 2018, 03:22 PM) *
...a slightly different problem: GEN light comes on strong with key on, engine not running, But then the GEN light glows very soft at idle, and then comes on stronger as RPMs build.

Post #36 (also on page 2 of now 7):
QUOTE(GregAmy @ Mar 25 2019, 09:58 PM) *

Quick follow up: alternator replacement solved it. I'm guessing a bad diode.

That's such a hateful job...

Replace the alternator.


Edit: print these out in color, and keep them in your manual. As an electrical professional, you can appreciate their value. I've got mine spliced together in a multi-fold so I can expand them out on the toolbox and work through any/all electrical issues...

http://web.archive.org/web/20140328013841/...al_diagrams.htm

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Gatornapper
post Sep 11 2019, 08:33 AM
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QUOTE(Spoke @ Sep 10 2019, 08:47 PM) *

QUOTE(Gatornapper @ Sep 10 2019, 09:52 PM) *

Mark -

The first comforting thing I've heard about that jumper - as the Porsche dealer did the carb conversion, the jumper definitely doesn't look like a shade-tree mechanic one, but a very professional one....


The jumper is well done and quite unique. The jumper on your 914 definitely stumped the band although it does work. SirAndy's solution is the one you want.

Put it on your list of things to correct. It is not as important as getting the alternator/VR working. WILL DO!

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GregAmy
post Sep 11 2019, 08:53 AM
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QUOTE(Gatornapper @ Sep 11 2019, 10:30 AM) *
If the alternator is bad, I want a technical explanation for why it passes all the tests except for the one that counts - working.

No one on this forum can provide that information to you.

A local rebuilder might...if you'd take the time to remove the alternator and bring it to them.
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Gatornapper
post Sep 11 2019, 10:51 AM
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I understand that Greg. And I've been thinking of going to rebuilder soon to ask that very question......before I remove the alternator.......

QUOTE(GregAmy @ Sep 11 2019, 08:53 AM) *


No one on this forum can provide that information to you.

A local rebuilder might...if you'd take the time to remove the alternator and bring it to them.

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Spoke
post Sep 11 2019, 12:34 PM
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I can understand questioning the health of the alternator in this situation.

However the simple DF to D+ test has the alternator producing 17V at the battery as expected for a good alternator.

An additional test with DF == D+ is to measure the voltage at D+. This should be equal to the battery voltage. This will go towards verifying the diodes are ok in the D+ as well as Battery outputs.

What is unexplained is why the VR produces no voltage at DF with the battery voltage at 12.x volts. The VR should be driving DF significantly if the battery voltage is in the 12.5V range.
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Gatornapper
post Sep 11 2019, 02:42 PM
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Spoke -

May have found the problem, and it is indeed in the alternator.

Met this afternoon with the best mechanic I know in central VA.

The key is what I mentioned at least twice earlier - why, when I hit DF with 12+v and get a full charge at the battery, does the charge quit when I remove the 12v?????

Once charged, the armature should retain its charge - mine does not. For some reason, the armature loses its magnetism - when it should retain it once charged.

My mechanic friend said he has seen this on other bad alternators many times - but no one has ever explained to him WHY it occurs. It renders the alternator bad - even though all the diodes are fully functional.

So I suspect that is what I am dealing with.

GN


QUOTE(Spoke @ Sep 11 2019, 12:34 PM) *

I can understand questioning the health of the alternator in this situation.

However the simple DF to D+ test has the alternator producing 17V at the battery as expected for a good alternator.

An additional test with DF == D+ is to measure the voltage at D+. This should be equal to the battery voltage. This will go towards verifying the diodes are ok in the D+ as well as Battery outputs.

What is unexplained is why the VR produces no voltage at DF with the battery voltage at 12.x volts. The VR should be driving DF significantly if the battery voltage is in the 12.5V range.

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Spoke
post Sep 11 2019, 04:05 PM
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QUOTE(Gatornapper @ Sep 11 2019, 04:42 PM) *

Spoke -

May have found the problem, and it is indeed in the alternator.

Met this afternoon with the best mechanic I know in central VA.

The key is what I mentioned at least twice earlier - why, when I hit DF with 12+v and get a full charge at the battery, does the charge quit when I remove the 12v?????

Once charged, the armature should retain its charge - mine does not. For some reason, the armature loses its magnetism - when it should retain it once charged.

My mechanic friend said he has seen this on other bad alternators many times - but no one has ever explained to him WHY it occurs. It renders the alternator bad - even though all the diodes are fully functional.

So I suspect that is what I am dealing with.

GN


About applying D+ to DF through the GEN light and getting 17V at the battery, then no output from the alternator when the D+ to DF connection is removed.

The alternator turning off when DF is disconnected from D+ (ie, interrupting the field current) is what one would expect if the VR is not in place or not functional. The alternator's output is somewhat proportional to the amount of field current and the rotational speed of the alternator. Take away the field current and the alternator stops.

There are lots of confusing data points with your charging systems for sure. I try to avoid swapping components w/o knowing exactly what is wrong. Especially the alternator which is not fun to remove.

There are 2 data points which are consistent with each other:
1) The alternator is not working (duh)
2) The VR is not producing voltage at DF

At this point I would be concerned with why the VR is not driving DF. I detailed a static test with engine not running to check the VR operation.

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Spoke
post Sep 11 2019, 04:07 PM
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Here's a good description of an automotive charging system like the 914. Text and link provided.

The Workings Of An Alternator

ALTERNATOR WARNING LIGHT

What does the little red light that says ALT, GEN or sometimes CHARGING mean when it comes on? Without being scientific, it means that either the alternator output voltage is lower than the battery voltage, or the battery voltage is lower than the alternator output voltage. If the light gets dimmer as you rev the engine up, then you most likely have a problem with the alternator. If the light gets brighter, then the battery is most likely the problem.

ALTERNATOR ROTOR

The rotor consists of a coil of wire wrapped around an iron core. Current through the wire coil – called “field” current – produces a magnetic field around the core. The strength of the field current determines the strength of the magnetic field. The field current is D/C, or direct current. In other words, the current flows in one direction only, and is supplied to the wire coil by a set of brushes and slip rings. The magnetic field produced has, as any magnet, a north and a south pole. The rotor is driven by the alternator pulley.

STATOR

Surrounding the rotor is another set of coils, three in total, called the stator. The stator is fixed to the shell of the alternator, and does not turn. As the rotor turns within the stator windings, the magnetic field of the rotor sweeps through the stator windings, producing an electrical current in the windings. Because of the rotation of the rotor, an alternating current is produced.

OUTPUT DIODES

A/C voltage is of little use in a D/C system, such as used in an automobile, so it has to be converted to D/C before it can be used. This conversion to D/C takes place in the “output diodes” and in the “diode trio.” Diodes have the property of allowing current to flow in only one direction, while blocking current flow in the other direction. The output diodes consist of six diodes, one pair for each winding. One of the pair is for the negative half cycle, and the other for the positive half cycle.

DIODE TRIO

The diode trio consists of three diodes, one per phase, which provides field current to the alternator regulator. This output will be discussed in more detail later in the “field current supply” section.

FIELD CURRENT SUPPLY

Field current supply is provided from two different sources – from the alternator itself, via the diode trio, and from the battery, via the alternator warning lamp. When you turn the key to “on”, the engine is not running and the alternator is not spinning. At this time, the voltage/current source for the field current is from the battery, through the ignition switch, and through the warning lamp. After the engine is started, and the alternator is up to speed, the output of the diode trio is fed back to the regulator, and serves as a source of current for the field current. At this time, the alternator is self sustaining, and the battery is no longer needed to power the automobiles electrical system.

REGULATOR

The regulator has two inputs and one output. The inputs are the field current supply and the control voltage input, and the output is the field current to the rotor. The regulator uses the control voltage input to control the amount of field current input that is allow to pass through to the rotor winding. If the battery voltage drops, the regulator senses this, by means of the connection to the battery, and allows more of the field current input to reach the rotor, which increases the magnetic field strength, which ultimately increases the voltage output of the alternator. Conversely, if the battery voltage goes up, less field current goes through the rotor windings, and the output voltage is reduced.

WARNING LIGHT

The alternator warning lamp travels a path to ground from the field current supply input to the voltage regulator. As a result, when the key is turned on, current flows through the warning lamp, through the resisters, transistors, and field coil in the alternator, and then to ground, causing the lamp to illuminate. Once the alternator is at full output its voltage will equal the battery voltage. At this time, with 12 volts on both sides, the lamp is out. If the alternator should fail, voltage from the diode trio would drop, and once again the lamp would light from the battery voltage. If the alternator output is only a little low, the lamp will be dimly lit. If the alternator fails completely, and the output voltage goes to zero, the lamp will be lit at full brilliance. Conversely, if the battery should fail, and the battery voltage drops, with the output voltage of the alternator on one side and the low battery voltage on the other, the lamp will also light. As stated earlier, if the light grows dimmer as the engine is revved up, it is because the alternator voltage is rising with the RPM, producing more voltage on the alternator side of the lamp. The closer the output voltage gets to the battery voltage, the dimmer the bulb becomes. By the same way, if the light gets brighter with increasing RPM, it is because as the alternator voltage increases, it is getting higher than the battery voltage. The higher the voltage with respect to the battery voltage, the greater the voltage difference across the lamp, and the brighter it gets.

The Workings of An Alternator
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Gatornapper
post Sep 12 2019, 07:18 AM
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QUOTE(Spoke @ Sep 11 2019, 04:05 PM) *

At this point I would be concerned with why the VR is not driving DF. I detailed a static test with engine not running to check the VR operation.


Precisely. Running your static test on 4 different VR's this am: Original, NOS, AC-Delco SS (probably made in China but copy of German one), and new Bosche loaned me by 914Sixer.

If none are producing voltage at DF, we know that's why system is not charging - and problem is neither in the VR nor the alternator.

914Sixer also loaned me a good relay board - that will be the next test if none of the VR's produce voltage at DF. What a gracious forum member Mark is. But we all already knew that, right?

GN
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VaccaRabite
post Sep 12 2019, 06:43 PM
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Is there any chance one of the VR sockets on the relay board have pushed through the potting and are not making solid contact with the VR? Maybe there enough that you can probe it, but not enough for the VR to really plug in? Its really hard to see it looking at the relay board, but easy to feel if you reach under the board.

Zach
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Gatornapper
post Sep 13 2019, 06:53 AM
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Zach -

Thanks man, but swapped a good relay board yesterday another member loaned me - no change. So relay board is fine.

The expensive Bosche VR he loaned me did produce a solid 13.1 volts at the battery too, but not 14.1, and the Gen light stayed on.

I only ran it for a few minutes, then put my cheap SS AC-Delco one back in and now the Gen light stays OUT! But voltage at battery is only 12.2 to 12.4. Drove car in city for an hour in heavy traffic, thinking when I got home the battery would be discharged in the 11 volt range.

Nope. 12.36 volts. Normal resting voltage on this new gel battery is 12.65, so it was down a little, but not much.

I retract what I said about alternator being bad. Spoke clarified that the armature is simply an electro-magnet with windings as they all have - and all electro-magnets lose their magnetism when no voltage is on the windings. So the armature needs voltage all the time to work. And the armature IS getting voltage because I do have a charging voltage of 12.2 to 12.4. Apparently this is sufficient for daytime driving with no other electrical loads.

So I may just run this VR until I drop the engine for a top-end rebuild in the next 6 or so months.......

GN

QUOTE(VaccaRabite @ Sep 12 2019, 06:43 PM) *

Is there any chance one of the VR sockets on the relay board have pushed through the potting and are not making solid contact with the VR? Maybe there enough that you can probe it, but not enough for the VR to really plug in? Its really hard to see it looking at the relay board, but easy to feel if you reach under the board.

Zach

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Gatornapper
post Sep 13 2019, 06:56 AM
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Going to put a volt-meter in the cabin. Can someone advise me on where an original volt-meter would get its positive signal? Where I should tap the wiring for a 12v signal that will switch off with the ignition?

TIA,

GN
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914Sixer
post Sep 13 2019, 07:04 AM
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Cigar litter is always hot.
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VaccaRabite
post Sep 13 2019, 08:37 AM
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QUOTE(Gatornapper @ Sep 13 2019, 08:53 AM) *

Zach -

Thanks man, but swapped a good relay board yesterday another member loaned me - no change. So relay board is fine.

The expensive Bosche VR he loaned me did produce a solid 13.1 volts at the battery too, but not 14.1, and the Gen light stayed on.

I only ran it for a few minutes, then put my cheap SS AC-Delco one back in and now the Gen light stays OUT! But voltage at battery is only 12.2 to 12.4. Drove car in city for an hour in heavy traffic, thinking when I got home the battery would be discharged in the 11 volt range.

13.1 is acceptable - the battery is charging. 12.2 - 12.4 isn't. You have resistance somewhere and it will strand you eventually... I was where you are now last summer.

At around 11.5 volts your car starts running rough running. By 10.6 or so your car is dead. but your flashers will still work while you wait for the tow truck. And then you get to post on the Flatbed thread.

Zach
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Gatornapper
post Sep 13 2019, 09:12 AM
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Just found this on Pelican's site for a rebuilt Bosche alternator - surprised I've never seen this issue before - this guy says the problem exists on multiple alternators he has......seems this would explain what's going on with my system. Of course, I won't know until I pull my alternator........
===================================

Andrew B.
October 25th, 2016
Rear cover can short circuit
This alternator doesn't come with the rear cover plate and wiring harness. You have to transfer those parts from your old alternator.

There is an un-insulated terminal on the back side of the alternator, labelled B+ (positive connection from the battery) That terminal can ground against the back cover plate, making a short circuit ground from the battery. The terminal has both a nut sticking up and a wide washer under the nut. I covered the washer with a ring of paper gasket material, held in place with a dab of RTV silicon, and then covered the nut with a small plastic cap, again held with RTV silicon. The Porsche parts diagrams show a gasket under the back cover plate. That would help space the cover up to clear this terminal, but that gasket was missing from my old alternator, and it is not included with this new one. I cut a new gasket from 1/16" paper gasket material and installed it under the cover. Checking the 3 or 4 old alternators I had in my parts collection, sure enough, they all have blobs or sealant or other somewhat jury rigged looking solutions to this problem. Bosch should really be providing an insulated cover for this terminal, or a back cover plate with more clearance."


GN
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Spoke
post Sep 15 2019, 06:47 PM
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With all the measurement of voltages being discussed around Gatornapper's charging issues, I decided to take a few measurements of my 914 in which the charging system is working as expected.

If a charging system (alternator, VR, battery) is being evaluated for some issue, one should always think about taking a "set" of measurements to get a good feel for the health of the system. That set would include:

1) Battery voltage
2) D+ voltage at VR or alternator plug
3) DF voltage at VR or alternator plug
4) D- voltage at VR or alternator plug

Each measurement is taken with respect a chassis hard point. Not the battery negative or engine or transmission. Use either the stud behind the relay board or the stud behind the battery.

I took a couple of sets of measurements today after a 10 minute drive. 4 sets of measurements were taken:

1) At idle w/o headlights
2) at 2k RPM w/o headlights
3) at idle headlights ON
4) at 2k RPM headlights ON

First set at idle w/o headlights.

VBAT: 13.5Vdc
D+: 13.5-13.8Vdc bouncing around
DF: 12Vdc
D-: -25mv

at 2k RPM w/o headlights.

VBAT: 13.6Vdc
D+: 13.95Vdc steady
DF: 5Vdc
D-: -66mv

at idle headlights ON.

VBAT: 12.6Vdc
D+: 13.5Vdc
DF: 11.3Vdc
D-: -31mv

at 2k RPM headlights ON.

VBAT: 13.4Vdc
D+: 13.6Vdc
DF: 6Vdc
D-: -120mv

All 4 sets of these measurements took less than 5 minutes total. Notice VBAT and D+ are always within 1V of each other. This indicates the 6 steering diodes pointing to VBAT and D+ are in good shape.

Since the magnetic field generated by the armature is rotational speed dependent, as the RPM increased the VR dropped the voltage to the field windings (about 12V down to 5-6V) to keep the output voltage constant.

Notice the voltage of D- increases with increased alternator load maxing out at -0.12V with lights on at 2k RPM.
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