Alternator / Idiot light NOT lighting up!

[brice]

Summary: idiot light lights up when connected to ground, does NOT light up when connected to D+ post of alternator. blown alt?

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My generator light is *not lighting* up when I turn the key -- and I know that both the oil pressure + gen light are supposed to come on, and the alternator will not send a charge if the idiot light is dysfunctional... Once I had a battery die because I forgot to hookup the blue "idiot wire" after changing the speedo cable!

I have a 1974 SB with a newer Bosch AL82 internally regulated alternator. When I installed it a few years back I removed the old external regulator, and spliced the green (alternator D+ wire) to the blue (idiot light wire) to accomodate for the internal regulated alternator (according to schematic here: http://www.thesamba.com/vw/forum/viewtopic.php?t=383271&highlight=idiot+light) The car has been a more or less reliable daily driver for 4+ years...

Here's what I've done:

1. I opened the engine and removed speedometer from dash so I can access.

2. I removed green/red oil pressure light wire from bulb (known working) and hooked the blue idiot wire to it -- still no light.

3. I ran a long wire directly from the D+ post of the alternator to the idiot light -- still no light.

4. I touched the end of this direct wire to the ground on the alternator -- it LIT UP.

So; the idiot builb lights up when connected to ground, and does NOT light up when connected to the D+ post of the alternator. Does this indicate a blown alternator? Any fix?

Many thanks as ever!

[lytnbug]

Which idiot light wire are touching to ground? I guess you know that one side of the bulb that is NOT the blue wire SHOULD be grounded. The blue wire is what causes it to come on with + volts from alternator/regulator circuit.
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'73 Fat Super Beetle
'78 Super 'Vert
'62 Std. Beetle

[brice]

[lytnbug]

[lytnbug]

[lytnbug]

I never stop. Ha. I found some more info and the path for the idiot light should go through the regulator AND the field coil. So, it could something as simple as bad brush(es).
_________________
'73 Fat Super Beetle
'78 Super 'Vert
'62 Std. Beetle

[brice]

lytnbug,

Thank you very much for helping with this problem! Pulling the alternator is a pain, but I guess something I need to do if necessary. Do you know if it's possible to pull out the brushes / internal regulator without removing the alternator? It is a new (@ 4 year old) Bosch AL82N.

Many thanks!

~ Brice

[lytnbug]

The brushes should be under the plate where the D+ plugs.

Not sure on the regulator. If it is like a domestic, it is usually mounted inside on one of the end plates for heat dissipation.
_________________
'73 Fat Super Beetle
'78 Super 'Vert
'62 Std. Beetle

[lytnbug]

I was looking at a picture of the brushes on partsgeek and they look to be a PITA to get to with the alternator installed and intact. But at least they sell these things. http://www.partsgeek.com/gbproducts/WC/17324-01023...oogle+Base Usually can't find these at regular VW parts outlets/stores.
_________________
'73 Fat Super Beetle
'78 Super 'Vert
'62 Std. Beetle

[lytnbug]

[brice]

Thanks so much for the info. I went ahead and pulled the brush holder which has the D+ post on top. Here's what I found;

The brush holder has springs which push the brushes down onto revolving metal in the alternator (I assume this is what generates/transfers voltage). 2 wires inside the alternator attach to the brush holder -- a red and a blue -- seen here:

When I touch the GEN/"idiot light" wire [that normally connects to the D+ post] to the BLUE wire in the alternator, it lights up. It also lights up if it touches ground [anywhere on the alternator case]. It does NOT light up if I touch it against the red wire in the alternator OR any of metal that the brushes rub against.

I made sure all connections were good and pressed the D+ "brush holder" (pictured below) back into its spot on the alternator. Still to GEN light.

I began to experiment & noticed that the GEN light comes on when the D+ post "brush holder" is rocked slightly towards you (so that the side towards the front of the car is up). I hear a clicking when it gets into this position, as if the [front?] brush spring engages or is lifted off the metal.

Is this "brush holder" (yes, I know it's the wrong word?) bad -- or maybe the regulator? It doesn't seem that this piece is doing the regulating -- and I don't seem to be able to get to the [internal] regulator (where I assume the red + blue wires are attaching).

Many thanks for your input! Here's pics of my "brush holder";

[lytnbug]

One possibility, and I had this happen to one of my alternators, is that the brushes get worn down so far that they don't make good contact with the commutator rings. I would sure try replacing the brushes first, especially since we know where you can buy them. If it were the regulator, rocking the assembly would not have the affect that it does.
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'73 Fat Super Beetle
'78 Super 'Vert
'62 Std. Beetle

[brice]

Lytnbug,

I'll try buying brushes for this & replacing. Thanks for the advice! It's strange, as this is only 4 years old, and I've heard that alternator brushes supposedly have 100,000+ mileage in their life (I've *maybe* put on 30?)

[lytnbug]

[brice]

The mounting screws appear to only anchor the plastic brush holder in place. I don't see any wire or path connected to them that would give the circuit ground. My fear is that something is blown in the interior regulator (which I cannot get to w/o taking the alternator apart)?? I am guessing that the blue & red wires that attach to the brushes go there?

Do my brushes look very worn down? I couldn't find anything at rockauto.com that resembled them. Does anyone else have photos of theirs (Bosch AL82N)?

Thanks!

[lytnbug]

[brice]

lyntnbug,

I somehow stumbled across this post last night:

http://www.thesamba.com/vw/forum/viewtopic.php?p=4506592

It strongly suggests that it's an Internal Regulator. The author was kind enough to point to where he bought his ($14.95 at autohaus AZ).

I'm going to re-examine the brush holder to make sure all solder points are intact. There's a metal clip that sticks out of the brush holder & contacts a thin piece of metal on the alternator case... but touching the idiot light D+ wire to its contact point does not light it up / give it ground? That seems to be the only feasible point. I'll supply more pics when I get back.

[scrivyscriv]

Curious if you got the issue resolved, and what fixed it.

Four years later...

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Robert in Memphis
Dünkelgrügen 1967 Java Green bug thread
Engine rebuild thread
If you're ever in the Memphis area, you are welcome to stop by for advice and help.