Thanks for the idea - I'll do that. But previously I've checked all grounding connections and they are all good. Completely refurbished the one from the battery negative terminal to the chassis......

Another good point to measure is from the alternator mounting strap to the chassis and to the engine case while running.....I'll do that one too. All should be way less than 1 volt.....really zero.

GN

Spoke - yes, GEN light is OFF until I turn on headlights, then on, but very dim.

I will check for zero resistance between the VR pins and the alternator pins -

Thank you.

If all is well with the relay board, I have a bad VR that came with car and a bad NOS one I just bought from a forum member - who will refund my money if I want. First I want to make sure the NOS one is bad as well.

AND I have a cheap (Chineses I suspect) one coming next week from Rock Auto I got just for a point of reference.

Thanks!

GN

Re: VR not working.

Both VR's I have get very hot - too hot to touch. So it seems that they are trying to work - lot of activity going on electrically to produce all that heat......

I had two original regulators that were tested as good at a auto electric shop and both of them would get hot when running. That may be why there is a hole in the relay board under the regulator, to let some air get in there.

I purchased a solid state regulator from BERU. and it works perfectly and does not get hot. you have to modify the mounting holes on the BERU unit and trim the plastic relay board cover for it to fit but when mounted you can't see the modification to the cover.

I think the BERU unit was $25-30

Thanks - would like to get one....

Checked BERU's site, cannot get to where I can purchase a unit......entered United States, and my zip code - got nothing......

Typically can't purchase products from companies' web sites ... need to purchase items from retail vendors

https://www.autohausaz.com/pn/12181365-9016...hgaAiXcEALw_wcB

Thanks Mark.

Ok, test results:

Relay board not the problem......zero resistance between the D+, D-, and DF at the VR contacts and their matching points at the cable to the alternator end. No corrosion or even dust at any of the contact points - but then I had cleaned them with electrical contact cleaner anyway.

Also, voltage between battery ground and engine while running is .007 volt......essentially nothing.

Ran separate ground from engine to chassis, no change in anything.

Only thing left is the VR as far as I can see things......

Long wait until next Tuesday.

GN

Maybe I missed in the thread but did you check voltage between the alternator body and the engine case? Should be zero.
The alternator grounds to teh engine through the mounting to the engine, unless someone has added a ground strap.
There have been a few cases of painted or powder coated alternator bodies and/or mounting brackets that were preventing a good ground for the alternator.

Good luck

Jim

Just to check: both VR's get very hot but both do not work and no charging is going on, correct? No charging means you see less than 12.6V while running.

It is odd that 2 VR's both do the same thing (get hot) but don't work. However when you short DF to D+ you get full charging from the alternator.

One more thing to check with engine off, check: remove the VR and disconnect the alternator cable. Then check resistance between D+ to DF, D+ to D- and D+ to D-. Just make sure there are no shorts on the relay board. All should be infinite.

Also measure resistance D+ to chassis; DF to chassis; and D- to chassis. All should be infinite although D+ might show some resistance as D+ is connected to the GEN bulb and to stuff on the other side of the bulb.

Again looking for shorts to ground. Just want to make sure there are no shorts on the relay board.

Good to check voltage from battery ground to engine is low. For the alternator, the important measurement is from the alternator case to battery ground/chassis. By measuring D- to chassis before you have done this test. See the schematic below. Notice the D- wire at the VR goes into the alternator and directly to ground. That ground is actually:

The alternator case to fan shroud to engine case to transmission case to transmission wire strap to chassis ground.

So measuring D- to chassis measures the total voltage drop of all those components. If you see less than about 0.2V drop from D- to chassis while the alternator is working, the alternator is properly grounded.

Keep in mind that without the alternator working, there is no current in the alternator to chassis ground so a zero volt reading would be expected even if the alternator ground is not good. The best way to ground the alternator is to run a wire from the alternator case to chassis. This is especially important if you have painted or powdercoated the fan shroud. Right Zach?

Jim - will check tomorrow, but checked all other places for a difference in potential with none.....glimpse of alternator I saw from below makes me think it is not original, but it wasn't painted......

All ideas appreciated.....

GN

Spoke -

Will run all suggested tests tomorrow - rain coming so working in shop/garage will be fine.

I am also going to run a new #6 Cu. ground wire from the battery chassis ground bolt to the shroud. Extra ground protection. Doubt it will do anything as I only got .007v potential between those two points today with engine running.

Fan shroud is original. Car has only 61 k original miles - judging by pedal wear that is accurate...also by repair records I have.

So when I check D- to chassis that's with the VR removed, correct?

I have this sneaky feeling that the new VR I'm getting next Tuesday will show the same results as the original one and the NOS one I just got.......

GN

You don't have to remove the VR for this measurement. The VR should be in the circuit. The alternator should be working though since a voltage drop here needs current to get a good measurement and that current is generated by the alternator when it is running.

Voltage here is V = I x R where I is current from the alternator and R is the resistance between the alternator case and chassis.



That's also my concern. This is why I asked you to do many resistance measurements on the relay board. There's not much in the alternator circuit (alternator, VR, GEN bulb, battery) but it has several connections which could cause issues namely the relay board.

Yeah. I was driving myself batty chasing a similar issue last summer. You could not detect the resistance without power going through the system.
The voltage drop was minimal, but it does not take much resistance in the dog house for the battery to get drained. Running a grounding wire from the alt housing to a clean chassis ground eliminated the issue for me.

Zach

Dumb question: if the VR is in place, where do I get a reading on D- ? Seems all connections are obscured, no available point for probe......

GN

Zach -

First running one to the shroud. Then checking for potential between alternator frame and engine. If that doesn't do it, then I'll run one to alternator frame.

So you had similar symptoms? So I'm not crazy?

Thanks!

GN

The D- signal can be found on the cable from the alternator. Below is my 914 showing the cable and its connector. You should be able to measure right on the connector with the VR left in place.

The VR I have was purchased at my local FLAPS and works very well. 14V all day.

This diagram shows which signals are which.

In this diagram, DF goes to DF, D- to D- and nothing else.

D+ goes to D+ then onto pin 2 of the 14 pin connector going to the cabin and to the GEN bulb.

I should have told you all I don't have regular problems. If they are regular, I fix them, no one knows. The plot thickened a lot today. And in my view gets worse.

1. Received new SS VR from Rock Auto today, AC Delco, is like the European one.
a. Bad news: no change. 12.12 volts at battery with engine running
b. Good news: GEN light is now reflecting reality - it glows. Higher I rev engine,
more it glows. Light is very dim at idle tho. NO Gen light with original VR or
NOS one I had.

2. I completely refreshed main ground between chassis and tranny. No change.

3. Using a very unusual bronze ground connector used by electricians I securely attached a new #6 Cu. wire to the alternator case and connected the other end to the ground/negative on the battery. NO CHANGE. Bummer. I was hoping Zach's solution would work.

While I did not take voltage readings while engine was running (Spoke - DUH - of course I can probe generator cable connections - brain was not turned on.....), I did take readings with engine off. DF and D- had infinite resistance to ground. D+ had 74 ohms.

4. Just to make sure I wasn't dreaming, I again removed the VR and jumped D+ and DF, and once again, got between 16.8 and 17 volts at the battery. So alternator HAS to be good, correct?

Ok, now taking readings at alternator plug terminals while engine is running.

Hoping someone has some new insights.....

Thanks to all for laboring with me through this mystery.......

GN

It makes me wonder if the VR is not starting because of insufficient current though the GEN light. Try this test. Pull out the gauge with the GEN light. Start the engine. Carefully touch a screwdriver across the GEN bulb. This is to force the VR voltage to battery voltage. See if the alternator starts up. This shouldn't damage anything.

Don't touch the screwdriver to the case When doing this.

Spoke -

D- to engine or chassis with engine running, VR in place: .01v

Nothing. Zip. Nada. Zero. Barely measurable.

GN

Ok, I can do that, but then I need someone else at my DVM to read the voltage at the battery, right?

I personally doubt this is the problem - the light comes on at a correct brightness (seems to me) when ignition is on, engine off. It would only get dim with first 2 VR's, but now seems to work correctly with the new SS VR. This would indicate to me that its wattage is correct.

How much trouble to take gauge out? Don't you pull the whole instrument cluster? It's with the Temp Gauge........

Gotcha on not shorting anything......

I'm leaning toward a bad relay board. The GEN lamp and relay board are about all that's left, aren't they?

I have another idea: I'll bring a 1 amp fused 12+ from the battery through an 1156 bulb to D+ on the alternator plug terminal. Or a smaller lamp.......

And just touch it to energize the armature.........

Whacha think?

GN

What we're trying to do with the shorting the GEN bulb is to provide more energy to the VR and armature circuit to get the alternator to start. Once it starts, the GEN light should go out and the alternator will start working. So you don't need anyone to check with a DMM.

The 1156 bulb will work as well. That's basically what you're doing with shorting the GEN light. The GEN gauge pulls out of the dash by itself. Just like the tach and speedo will pull right out. Takes a little wiggling to pull it out. Sometimes the rubber gasket stays on the gauge and sometimes the rubber gasket stays on the dash.

The 1156 is a good idea. Just touch it from the battery to D+. This will provide a lot of current to the armature and should start up the alternator.

About the grounding, that you can get 17V on the battery when you short D+ to DF is a good indication that the ground is at least ok.

Spoke -

Ok, let's assume that jumping 12+ to the armature does activate the alternator, and it's charging. Now what?

Or, let's assume that jumping the 12+ does nothing - now what?

Wondering where we go from either one.....

TIA,

GN

What we're trying to do with the shorting the GEN bulb is to provide more energy to the VR and armature circuit to get the alternator to start. Once it starts, the GEN light should go out and the alternator will start working. So you don't need anyone to check with a DMM.

The 1156 bulb will work as well. That's basically what you're doing with shorting the GEN light. The GEN gauge pulls out of the dash by itself. Just like the tach and speedo will pull right out. Takes a little wiggling to pull it out. Sometimes the rubber gasket stays on the gauge and sometimes the rubber gasket stays on the dash.

The 1156 is a good idea. Just touch it from the battery to D+. This will provide a lot of current to the armature and should start up the alternator.

About the grounding, that you can get 17V on the battery when you short D+ to DF is a good indication that the ground is at least ok.
[/quote]

At this point, we're just testing things to try and get the alternator/VR working.

Another new VR didn't do anything which means the VR is not the issue. Something else is and we need to uncover what that is.

Do the 1156 test and see what happens. If the alternator starts up and keeps running, then you know the alternator/VR can run.

Adding information from owners manual. Please read information. Your last VR has a problem.

Mark - yes, I know this - so I have 3 bad VR's? 2 bad new ones in a row? One I got yesterday is SS too.......doubt it is bad.......

Belt is tight BTW.....

Understand and went through all this too.....except hitting DF with a full 12+v, which I'll do tonight......

https://www.pelicanparts.com/techarticles/9...roubleshoot.htm

Thanks,

GN

I would say the Bosch ones are ok. Is the alternator harness the original?

About the 1156 bulb with 1A fuse; the 1156 bulb will be the fuse and the load. The 1A fuse isn't needed as the 1156 bulb when put across 12V will burn about 2A.

Waiting to see what happens with this test. This will see if the alternator/VR will start up with significantly more current via the 1156. If the alternator/VR does start up, then the 1156 bulb will go out. If the alternator/VR does not start up, then the 1156 bulb will continue to light.

I would say yes.

But remember, it puts out full voltage and more when D+ & DF are jumped - on that harness......if the harness were bad, I don't think you'd see that.

Somehow the armature is not getting excited.

GN

Also doing this from Pelican's site: To trouble-shoot the problem, you need to check the various sections independently. Thus the first check: Connect +12 volts from the battery to the DF terminal on the relay board. This is the maximum field current situation, and should result in maximum output of the alternator. Note that this checks the B+ diodes, the alternator windings, and the common diodes. It does NOT check the D+ diodes.

But, essentially, this is duplicating the test with the 1156, and just energizing the armature from another route - directly on the DF wire instead of through the switch in the VR......

GN

Post I just made on Pelican's forum:

Greg -

Did your test. Plugged VR directly into alternator harness. Hit D+ with other side of lamp with 12+ on the opposite side. Lamp lit up - just like dash light - as it took the place of the dash GEN light in the circuit. Still no charging. 12.2 v at battery.

So clearly something is wrong, and it's not in the relay board or dash light circuit.

AND YET, using the 2 tests in this Pelican article,

https://www.pelicanparts.com/techarticles/9...roubleshoot.htm

The alternator checks out fine.

Test 1 "checks the B+ diodes, the alternator windings, and the common diodes. It does NOT test the D+ diodes". I hit DF with 12+ volts, and the system charged at full normal voltage: 14.1 volts.

But as soon as I removed the 12+ v from DF, the charging ceased. Once the armature is energized, shouldn't it stay energized?

Test 2, we know, tests the D+ diodes and "D+ portion of the system", by jumping D+ and DF - my system also passed this, producing 17+ v at the battery.

So what part of the system is failing? I can't see how it is the harness - as in both tests 1 and 2 full charging voltage is being produced at the battery....using the existing harness.

Seems to me the problem is indeed inside the alternator - as it will not retain its charge on the armature once charged. Something is preventing the armature from retaining its charge......all other things seem working properly.

Any insight and wisdom is greatly appreciated.

GN

You can't use just any light for the alternator light. It has to be a particular bulb to make the circuit work.

If you can connect DF to the positive battery post with the engine running, and get 17+ volts, then the alternator and harness is good. I would change the voltage regulator. Get a Bosch regulator, not some aftermarked reproduction.

Clay -

The 2nd VR I tried is NOS I got from a reliable forum member. It didn't work.

I only got the aftermarket one because it didn't work.

So you think I should buy a 2nd Bosch VR, only a modern one? How much are they? About $200, right?

Cannot see why the new SS VR I just got shouldn't work......

Pretty sure my GEN bulb is original, but will check it tomorrow - know it has to be 2 watt.

Thanks,

GN

Clay -

The strong implication of this statement in the Pelican article, "Too low a wattage bulb will not supply enough field current for "bootstrap" operation to be reliable. The Bosch book that I have states that the lamps must be at least 2 watts for 12 volt systems.", is that a higher wattage bulb, like I used in my test, should be no problem.

The problem is with a lower wattage bulb.

GN

Did you do the test with the 1156 bulb across the GEN light or across battery to D+? If so, what happened?

Yes. Nothing happened. Did not energize the armature, no charging, light went on and stayed on - just like GEN light......

As wattage of bulb was more than 2 watts, the filament being a lower resistance, the voltage hitting the armature would have been higher than that of the 2 watt Gen bulb - and the armature should have been excited and produced a charge.

HOWEVER, remember - when I hit DF with a full 12 volts - the system charges to a full 14.1 volts as it should........but as soon as you remove the external 12v to DF, the charging ceases. Once energized, the armature should stay excited, producing a charge.

So I'm thinking the problem is in the armature.....perhaps a break in insulation that allows leakage of the voltage. I.e., a short.

GN

OK, so a higher power GEN light doesn't get the VR started...


You applied the 1156 from 12V battery to D+, not to DF. DF energized is the responsibility of the VR. If the VR is not working, applying 12V to D+ will not energize DF.


Did you do this with the VR in place? Once you remove 12V from DF, if the VR is not operating, the voltage at DF could go to zero and the alternator will not function.



Your previous test seems in conflict with a bad armature as you were able to get 17V at the battery with the armature initially being driven with the GEN light:




It still seems like the VR is not starting up. I would be curious to know the voltages at the VR when running. The VR I have on my 914 has a plug and wires connecting to the VR thus I can measure voltages right on the VR plug. They should be the same as the voltages on the alternator plug.

Here's another test: With VR in place, start engine then short DF to D+ with the 1156 bulb. What you'd be doing is simulating the VR pulling up on DF as it should but seems it isn't. If the battery voltage goes up, then the alternator should be good.

Good idea. Will do.

What is strange to me is that once armature is excited/energized, it won't stay energized - or so it seems. This should not be. As the voltage across the GEN lamp is zero with a working VR and alternator once system is running, the initial exciting of the armature is enough. Correct?

Spoke - thanks for hanging with me on this. Thanks for the patience. Very frustrating for me - fixing electrical problems is my strong suite, and this is the first time ever I haven't found what is wrong and corrected it in my long life. I think there is something here about this system I am not seeing. But in actuality, the circuitry is very simple - as you well know.

At this point I'm suspecting one of the alternator diodes has gone bad.

I'd cut to the chase and try another alternator. Maybe another local member has a (known good) spare that you can try & buy

Mark -

Totally understand - but if one of the diodes were bad, I don't see how the alternator could put out a full 17+ volts on the test jumping D+ and DF, which my alternator did.

Unit also put out full 14.1v on other diode test......

I think something else is going on. Some think only the $200 Bosch VR will fix things.

Don't know anyone with an good alternator. If I have to pull it, pretty sure I can rebuild it myself.

Thanks,

GN

An easy way to test for burned diodes is to remove the VR and short DF to D+.

The alternator will produce maximum output.

At this point if all diodes are good, the battery voltage to chassis should equal the D+ voltage to chassis.

You need to know if the alternator is doing anything.

You will know immediately once DF is shorted to D+. The engine will suddenly have the full load of the alternator dragging on it and RPMs will drop. Using your meter should show 16-18 volts at idle this way. Don't do this longer then needed though, as you will be overcharging your battery.

Zach

Memories guys? Jerry & Zack - Long ago I jumped D+ & DF and did get full 17v at the battery and reported on that numerous times to support my view that the alternator is fine. Even ran the test multiple times.

Also put 12+v to DF as the Pelican article suggests to check all the other diodes, and it too produced a full 14.1 v at the battery, showing all the other alternator diodes are good.

Today verified that the GEN light is indeed 2 watts - and just for the fun of it installed a new 2 watt lamp.

No change.

Thanks,

GN

I would like you to repeat this test and measure:

1) Battery voltage to chassis
2) D+ voltage to chassis
3) GEN light goes out

We're looking to see that VBAT and D+ are exactly the same. This would verify that the diodes in the VBAT path and D+ path are functioning.

If VBAT not equal to D+, then diodes in the alternator may be suspect. The GEN light might be lit as well if VBAT != D+.

If VBAT == D+ AND GEN light goes out, then likely the alternator is ok. This also means that the GEN light provides enough current excite the armature and to bootstrap the alternator into functionality.

If the alternator passes this test, then we suspect the VR AND/OR the wiring to/from the VR. Generating a voltage at DF to excite the alternator is the responsibility of the VR. Thus my request to measure the voltages D+, DF, and D- to chassis directly at the VR connector. If D+ is less than 13-14V, then the VR should raise the voltage at DF to further excite the alternator to produce voltage/current.

No voltage at the DF pin on the alternator connector with D+ less than 14V and D- around zero volts points to the VR and its wiring.

Here's a way to do a quick test on the VR. I just did this on my 914. The goal is to see if the VR will raise the voltage at DF.

There are 2 parts to this test. This is part 1; Isolation of the VR.

The set up for test 1 is as follows:

1) Remove the connector to the alternator. This will remove the load on DF and isolate the VR. This also removed the ground connection to the VR which will be reconnected in step 4.

2) Remove the power to the FI ECU (if you have FI). If you have carbs, remove the ground jumper from the FI connector on the relay board. This jumper powers the fuel pump. We want the fuel pump off.

3) Remove the 12V connector to the ignition coil. This keeps the points/Pertronix/electronic points from being powered. If you have some other electronic ignition system, remove 12V power from the unit.

4) Ground the D- pin at the alternator connector on the relay board. When you disconnect the alternator plug, the VR loses its ground. I used the jumper wire from the FI ECU connector for the fuel pump to ground D- as shown below.

5) Turn the ignition key to ON.

6) Observe that the GEN light is OFF.

7) At the alternator socket on the relay board, measure D+ to chassis and DF to chassis. On my car, I measured about 10.5V at both D+ and DF.

8) Turn the ignition key to OFF.

Notes:
At step 7, the VR on my 914 sensed only 10.5V and attempted to drive the armature via DF to a high voltage.

The resting voltage of the battery on my car was 12V. This seems low although all exterior marker lights (LEDs) were on as I've rewired the lights to come on when the ignition is ON.

Part 2 of the VR test is to check the D+ and DF voltages with the alternator connected to the VR.

The set up for test 2 is as follows:

1) If test 1 was just run, all wires are connected as needed. If test 1 was not run, do steps 1 through 4.

2) Remove the ground jumper on the D- pin at the alternator connector on the relay board.

3) Connect the alternator cable to the alternator connector on the relay board. Now the alternator/VR are connected as in the running condition.

4) Turn the ignition key to ON, do not start the car.

5) Observe the GEN light on brightly.

6) At the alternator socket on the relay board, measure D+ to chassis and DF to chassis. On my car, I measured about 2.3V at D+ and 1.5V at DF.

7) The test is done. Reconnect the FI ECU or fuel pump connections. Reconnect the ignition wires to the coil.


Notes:
On my 914, very little voltage was present at D+ and DF since most of the voltage was dropped across the GEN light. Even with only 2.3V at D+, the VR still raised the voltage DF to 1.5V.

Once spinning when starting the car and initial engine running, this little voltage to DF should be enough for the alternator to generate at least a few more volts at D+ which will drive the DF (armature) even higher in voltage thus producing more voltage until the alternator/VR reaches 13-14V and the system is now in regulation.

Ok, will do today.

One additional bit of info: GEN light is OUT when engine is idling.....only comes on with rpm increase, more rpm = brighter GEN light. Bat to chassis when light is OUT is about 12.2 on a fully-charged 12.6 v resting battery.

GN