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> Alternator question., Not Charging.
Spoke
post Sep 4 2019, 07:24 PM
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QUOTE(Gatornapper @ Sep 4 2019, 07:28 PM) *

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


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?



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Gatornapper
post Sep 4 2019, 08:09 PM
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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

QUOTE(jcd914 @ Sep 4 2019, 05:53 PM) *

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

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Gatornapper
post Sep 4 2019, 08:23 PM
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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
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Spoke
post Sep 5 2019, 04:15 AM
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QUOTE(Gatornapper @ Sep 4 2019, 10:23 PM) *

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


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.

QUOTE

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


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.
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VaccaRabite
post Sep 5 2019, 07:58 AM
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QUOTE(Spoke @ Sep 4 2019, 09:24 PM) *

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?


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
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Gatornapper
post Sep 5 2019, 10:59 AM
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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
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Gatornapper
post Sep 5 2019, 11:03 AM
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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

QUOTE(VaccaRabite @ Sep 5 2019, 07:58 AM) *


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

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Spoke
post Sep 5 2019, 03:58 PM
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QUOTE(Gatornapper @ Sep 5 2019, 12:59 PM) *

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


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.


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Spoke
post Sep 5 2019, 04:02 PM
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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.


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Gatornapper
post Sep 5 2019, 04:54 PM
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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
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Spoke
post Sep 5 2019, 05:41 PM
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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.
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Gatornapper
post Sep 5 2019, 06:05 PM
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Spoke -

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

Nothing. Zip. Nada. Zero. Barely measurable.

GN
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Gatornapper
post Sep 5 2019, 06:12 PM
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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?


QUOTE(Spoke @ Sep 5 2019, 05:41 PM) *

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.

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Gatornapper
post Sep 5 2019, 06:18 PM
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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



QUOTE(Spoke @ Sep 5 2019, 05:41 PM) *

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.
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Spoke
post Sep 5 2019, 06:41 PM
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QUOTE(Gatornapper @ Sep 5 2019, 08:18 PM) *

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?


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.
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Gatornapper
post Sep 5 2019, 07:05 PM
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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.
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Spoke
post Sep 5 2019, 07:29 PM
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QUOTE(Gatornapper @ Sep 5 2019, 09:05 PM) *

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



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.
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914Sixer
post Sep 6 2019, 02:54 PM
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Adding information from owners manual. Please read information. Your last VR has a problem.


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Gatornapper
post Sep 6 2019, 03:34 PM
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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

QUOTE(914Sixer @ Sep 6 2019, 02:54 PM) *

Adding information from owners manual. Please read information. Your last VR has a problem.
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914Sixer
post Sep 6 2019, 03:54 PM
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I would say the Bosch ones are ok. Is the alternator harness the original?
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