Alternator question., Not Charging. Options

[Olympic 914]

On Thursday took the alternator to the local FLAPS and had it tested , they said it had a fault but it passed 3 of 4 tests. still no good. so I ordered another alternator and took the bad one to a reputable local auto / truck electrical shop planning to have it rebuilt and keep as a spare... well they tested it and it and said it was good ??? (IMG:style_emoticons/default/confused24.gif) and all my regulators tested good also.

Reinstalled it and it worked for two seconds, count .. one thousand one, one thousand two. before the alt light came on again.... (IMG:style_emoticons/default/mad.gif) So I figured I was out of luck for Hershey. No sense going if I can't take the car.

At 10:15 on Friday morning the Flaps called and said the new alternator came in.so I hurried down to pick it up, Installed it, I had a working charging system now, and after a quick ride around the block, headed off to Hershey.

Where I picked up ANOTHER regulator. this one a Bosch solid state.

So 450 miles later everything is working fine.... Finally...

I guess the alternator was the problem all along but intermittently working, Now I have a bunch of spare regulators and a new Bowlsby wiring harness.

Thanks for your help and suggestions.

Tom

[Spoke]

(IMG:style_emoticons/default/beerchug.gif)

[GregAmy]

That post #15 is a gem...

Camping onto this one for 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. Battery is getting ~13.5 volts when running.

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.

Check. I get around 15.5V at idle and up to 17+ as I rev it up.

To check the D+ portion of the system, it is necessary to find out if the D+ output can produce enough current to drive the alternator to full output. To do this, short the D+ and DF terminals on the relay board. This will provide the maximum field current to the alternator that the alternator ITSELF can supply

Check. Same as above, 15+ V at idle and 17+ as I rev it up.

Problem is, I can't check to see if it extiguishes the GEN light, because my GEN light is not on with the voltage regulator removed. It'll only come on with the regulator installed. This makes sense, because looking at the wiring diagram the ground side of the GEN light is through the voltage regulator; it's blocked by diodes at the alternator from grounding.

Does everyone else's GEN light come on with key on and engine off when the VR is removed?

I did some further checks. Pulled the combo gauge out and measured voltage at the GEN light housing. With the engine off I'm getting 0V across the terminals, but with the engine running I'm getting ~2V at idle with the blue (D+) wire hotter than the red (system) voltage wire, rising to nearly 4V at revs. Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+.

That would certainly explain the glowing bulb.

So here's the key question: what is supposed to be at D+? I'm guessing the same as system. B+ is being regulated, so the rest of the car is getting the proper voltage, it's just the D+ wire that's too hot. Unfortunately, I don't know enough about these systems to understand why that could happen.

Since the rest of the car is not overcharging it seems safe to drive, and it'll still glow bright if I fail the alternator, but I'd prefer to not ignore it.

I REALLY don't want to replace the alternator in this thing...Thoughts appreciated.

Greg

Edit: an added data point. I swapped out the Hella solid state VR for a resgular Bosch VR of unknown provenance. Now I'm getting 13.5 on the D+ side and 12.2 on the B+ side. I might just buy a new VR from a local FLAPS and see if that resolves it.

[Spoke]

Does everyone else's GEN light come on with key on and engine off when the VR is removed?

Yes, the light is on with key on and engine not running and off with VR removed.

Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+.

That would certainly explain the glowing bulb.

I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed? At idle and 2k RPM. The difference between the voltage at S9 and D+ is the voltage across the GEN light.

These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation. This could point to alternator diode issue although I wouldn't replace the alternator unless sure it's not the VR. It would be convenient to swap the VR for a known good one before buying a new VR.

So here's the key question: what is supposed to be at D+?

D+ doesn't matter in this case. D+ is the voltage across the armature to provide field current for the armature coil. It will vary with load. The VR controls this.

Since the rest of the car is not overcharging it seems safe to drive, and it'll still glow bright if I fail the alternator, but I'd prefer to not ignore it.

Agreed it should be ok as long as the battery voltage stays above 13V and below 15V.

[GregAmy]

Yes, the light is on with key on and engine not running and off with VR removed.

How? Look at the wiring diagram: if you remove the voltage regulator then to what circuit will the GEN lamp ground? The diodes in the alternator should stop it from being grounded there, leaving only the circuits in the voltage regulator...so, to the wiring diagram, the GEN light should not be on with the VR removed and the key on.

Have you observed it that way yourself? If not, give it a try.

I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed?

Exactly as I wrote above: "Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+."

Direct to battery using the same ground is within 0.2V of S9, as measured on the S9 side of the GEN light housing.

These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation.

"Should".

Ain't.

[Spoke]

Yes, the light is on with key on and engine not running and off with VR removed.

How? Look at the wiring diagram: if you remove the voltage regulator then to what circuit will the GEN lamp ground? The diodes in the alternator should stop it from being grounded there, leaving only the circuits in the voltage regulator...so, to the wiring diagram, the GEN light should not be on with the VR removed and the key on.

Have you observed it that way yourself? If not, give it a try.

I'm not sure I follow your measurements. What are the 2 measurements at S9 and D+ both to ground at the same condition with the VR installed?

Exactly as I wrote above: "Measured to ground, I'm getting system (~13.5V) voltage from the S9 fuse and ~15.5V at idle and ~17.5V (max alternator output) at the blue D+."

Direct to battery using the same ground is within 0.2V of S9, as measured on the S9 side of the GEN light housing.

These 2 voltage come from the 2 steering diode pins on the alternator which derive voltage from the same stator windings. They should always be the same during operation.

"Should".

Ain't.

I re-read my post and I had a few things wrong.

= With VR removed and engine not running, S9 is battery voltage (12.6V). The load looking into the D+ wire is infinite since the VR is the only load. and with the VR removed, electrically you only see the cathodes of the 3 alternator diodes. The GEN light doesn't light since current cannot flow into the cathodes of the 3 diodes.

= I said the voltage at D+ doesn't matter. I had confused D+ with DF. D+ should be exactly the same as the battery voltage. DF is variable with load and is controlled by the VR.

= About the measurements, here's what I think you've measured with the VR INSTALLED:

At idle:
V(S9) V(D+)
13.5V 15.5V

At elevated RPM
V(S9) V(D+)
13.5V 17.5V

Or are these numbers with VR REMOVED and D+ directly connected to DF?

[euro911]

I have several 'unknown condition' units I need to check out. I took one to Autozone several years ago and they said their machine didn't have the correct connector to test a type-4 alternator (IMG:style_emoticons/default/screwy.gif)

[GregAmy]

= About the measurements, here's what I think you've measured with the VR INSTALLED:

At idle:
V(S9) V(D+)
13.5V 15.5V

At elevated RPM
V(S9) V(D+)
13.5V 17.5V

Or are these numbers with VR REMOVED and D+ directly connected to DF?

I am going to check these again tonight. But the S9 and D+ measurements at the GEN bulb housing were with VR installed; the only VR-out checks I did were for the tests in post #15, where I connected B to D+ and jumped D+ to DF; both tests showed max alternator output, ~17.5 volts.

I wish I knew alternators better (that's some serious magic, like CV joints and rotary engines) but it makes no sense that I'm seeing system/battery voltage on S9 but what seems to be max alternater output on D+.

More data tonight.

[GregAmy]

= About the measurements, here's what I think you've measured with the VR INSTALLED:

Prior to start up
12.15V at the battery.

Voltage between from combo gauge housing (my ground inside) to battery 12.15

Key on, removed bulb:
11.83V between combo housing and red/white wire
0V between combo and blue wire

So my S9 circuit has a dirty connection somewhere, I'm losing 1/2V to the combo gauge.

Bulb back in, start car:
13.35V battery to combo gauge housing

13.32V between combo housing and red/white wire @ idle
~15.5v between combo housing and blue wire @ idle
Bulb glowing slightly

13.51V between combo housing and red/white wire @ revved
17.34V observed between combo housing and blue wire @ revved
Bulb glowing brighter, but not as bright as key on engine off.

Reminder: when I tested Battery to D+ and DF to D+ I got max alternator voltage both times.

So why is D+ showing max alternator output voltage when it's supposed to be the same as B+?

I'm'a gonna hit a FLAPS for a new voltage regulator, not really hopeful but fingers crossed.

[GregAmy]

Aaaaand a new voltage regulator...

...didn't resolve it. Same problem. Wish I understood alternators better so I could understand the problem, but oh well. And I get to replace the alternator pigtail with a new one.

At least now I have a spare VR. Odd one too, from Echlin, remote mounts.

Who makes our preferred alternator so I won't have to do that job again? I've done it once before and I remember it was a fiddly job.

Dammit.

[Spoke]

Bummer. I didn't think the VR was at fault but it is an easy swap to find out.

Are all the ground straps (Battery to chassis; chassis to transmission) clean and tight?

[GregAmy]

Yep. All grounds and battery cables replaced by me a couple years ago.

Have not replaced the alternator pigtail though. I wonder if that's accessible with the alternator in the car?

[dangrouche]

Yep. All grounds and battery cables replaced by me a couple years ago.

Have not replaced the alternator pigtail though. I wonder if that's accessible with the alternator in the car?

the pigtail at the alternator end needs the alternator removed, and the metal cover shield removed as well. (IMG:style_emoticons/default/sad.gif)

HERE IS METHOD TO TROUBLESHOOT THE INSTALLED ALTERNATOR:
I did have a complete functional alternator assembly(alternator with the pigtail connected). I attached an alligator clip to the "extra alternator" body and grounded it to the car. I also did the same by connecting the positive terminal of the the external alternator to the car battery terminal. I plugged in the pigtail of the extra alternator onto the relay board. I switched the ignition key to the "on" position. I looked at the idiot light to see whether it glowed or not. (It did not glow with the installed alternator. ) The idiot light DID glow with the extra alternator, which meant installed alternator was failed (diode or brushes).

At least this way, I did not have to go to the trouble of pulling and testing the installed alternator. In the end, I rebuilt the installed alternator for $15 with a pair of alternator brushes from RockAuto.

[GregAmy]

the pigtail at the alternator end needs the alternator removed, and the metal cover shield removed as well. (IMG:style_emoticons/default/sad.gif)

Yeah. I had the race car on the lift so looked it over last night and it needs to be removed.

I've got a spare alternator on the bench, one removed some time ago, so I'm looking around to see if I can find someone to rebuild it. I'm in no rush; as noted before, best I can tell the only thing connected to the 17V on the D+ side is the GEN lamp, and with system at 13.5V it won't hurt anything for now while I get a replacement lined up.

[dangrouche]

https://www.aspwholesale.com/index.php

here is a website that sells the bearings and brushes parts if you are up to rebuilding it yourself

[GregAmy]

Camping onto this one for 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. Battery is getting ~13.5 volts when running.

So why is D+ showing max alternator output voltage when it's supposed to be the same as B+?

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

That's such a hateful job...

[worn]

Camping onto this one for 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. Battery is getting ~13.5 volts when running.

So why is D+ showing max alternator output voltage when it's supposed to be the same as B+?

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

That's such a hateful job...

Maximum alternator output is triggered when you bypass the voltage regulator. The battery voltage is the same as the alternator voltage because the two are coupled by large wires. The alternator pushes charges into the battery, and the battery pushes back. The voltage produced by the battery matches the voltage produced by the alternator.

Have no good explanation for the charging light.

Haven’t much liked pulling and replacing the alternator either...
At home or far afield. I will say that Ockteenerfest is a good place to get parts though...

[GregAmy]

Maximum alternator output is triggered when you bypass the voltage regulator. The battery voltage is the same as the alternator voltage because the two are coupled by large wires. The alternator pushes charges into the battery, and the battery pushes back. The voltage produced by the battery matches the voltage produced by the alternator.

Have no good explanation for the charging light.

It makes more sense if you read the back story (this page); I didn't quote it all because it's tedious...but short version, battery voltage (B+) was 13.5V but D+, the wire going to the dash gen light, was max voltage at 17.4V at RPM. They're supposed to be the same. So because D+ was more than B+, the gen light came on. It was dim at idle and got brighter with revs because the alternator was putting out more D+ with more RPM, while the voltage regulator was controlling B+ around 13.5 (4V differential).

The D+ wire only goes to the gen light, so it didn't hurt any systems to run it that way all last year. But it was an annoyance. I have the engine out of the race car for freshening so I chose to install its alternator into the street car, given the race car doesn't use the gen light or wire at all...but it might make a lot of sense to get it rebuilt before installing on the engine, since it's such a hateful job to replace it later...

[DRPHIL914]

Camping onto this one for 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. Battery is getting ~13.5 volts when running.

So why is D+ showing max alternator output voltage when it's supposed to be the same as B+?

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

That's such a hateful job...

Greg,

Glad you solved it. My issue was the lacke of a good ground due to the fan housing being powder coated , a new ground wire direct from the alternator to the body solved it. Something to keep in mind if you ever paint your engine tin and fan shroud!
I think it was Zach who had a similar issue that suggested this to me.

Phil

[VaccaRabite]

Greg,

Glad you solved it. My issue was the lacke of a good ground due to the fan housing being powder coated , a new ground wire direct from the alternator to the body solved it. Something to keep in mind if you ever paint your engine tin and fan shroud!
I think it was Zach who had a similar issue that suggested this to me.

Phil

Yup. powder coating the doghouse makes it look good, but sucks for the alternator. I chased my tail over that for a LONG time last summer.

Zach