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AL82 Alternator Hack
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telford dorr
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PostPosted: Sun Jan 08, 2017 7:44 pm    Post subject: AL82 Alternator Hack Reply with quote

Note: this is a hack. If you are a purists (or professional mechanic), DO NOT read this post. It will make you crazy. And we surely don't want that.

So, what kind of evil thing are we doing? We're converting an internally regulated AL82 alternator to an externally regulated one.

Why, oh why, would one want to do that?

Well, suppose you're Robbie, and you're 85 miles from nowhere, and your alternator just chose this place to take a dump. Also, suppose you have (somehow) determined the problem is the regulator, and you just happen to have one with you, and you also have wire, terminals, tools, and know-how. And you really don't want to pull the engine. So, is there a way around this? Can it be fixed without an engine drop?

Well, if you're Robbie, you drop the engine. If you're a normal person, or an old fart like me, you can try 'Plan B'. Here's plan B:

It just so happens that the brush holder on an AL82 can be removed with the engine in the car. So you remove the nasty red battery wire from the alternator lug and insulate it with some tape. (A more reasonable person would disconnect the battery, but then I'd have to reprogram a dozen stations on the radio which just got its power cut, and we're in the middle of nowhere, and can't receive most of them out here anyhow..) Now you remove the three screws holding the brush holder into the alternator, carefully wiggle it up, then unplug the two regulator wires. Now the brush holder can be removed.

If you inspect the brush holder, you will see that one of the regulator wires connects to the terminal which goes to the GEN/ALT dash indicator and one of the brushes, and the other regulator wire only goes to the other brush. This is the connection we have to get outside the alternator, if our scheme is to work.

Important note: we are going to modify a NLA part. If we screw up, we will likely only get another one attached to a (questionably) "rebuilt" alternator. And probably have to do an engine pull. So, if you try this, don't screw up. I just happened to have a second, very dead alternator handy, so I used its brush holder. The risk was low.

If you inspect the landscape around this second regulator connection, you will see that there is quite a bit of open real estate - enough that we could drill a hole without interfering with anything. I picked a spot that is little more than half a screw head away from the point where the brush solders onto the terminal, and drilled a 3/32" hole. I then (carefully!) tapped the hole for a 6-32 screw. I cut a solder lug (or bit of brass, whatever you have) to fit between the screw head and the brush solder point.

Image may have been reduced in size. Click image to view fullscreen.


Carefully tighten the screw, and then solder the lug to the brush holder eyelet.

Image may have been reduced in size. Click image to view fullscreen.


On the outside of the brush holder, we're going to install a 1/4" blade terminal (or a piece of fabricated brass from the hobby store (which just happens to be located out in the middle of nowhere, where we are). It is attached with a #6 star washer and a 6-32 nut (with a drop of Loctite, just to be sure). It should look like this:

Image may have been reduced in size. Click image to view fullscreen.


Now, put some shrink tubing on the old, abandoned internal regulator wires so that they don't get uppity and short against something, and carefully stuff them back into the alternator and forward of the hole. Now reinstall the modified brush holder with the three retaining screws. Reattach the dangerously sparky red wire back onto the alternator lug, and tighten. The alternator part of the job is done.

Now we have to fabricate a short harness to connect our external regulator with the modified alternator. You will need three wires (16 AWG):

- a wire from the original alternator ALT indicator lug
- a wire from the new lug we just added
- a ground wire from the ground screw on the alternator case.

The first wire needs a male and a female terminal, one to the alternator (female), and the other to the ALT indicator wire (male). Both of these terminals are at the alternator end of the wire, with maybe a two inch wire section between them. The other end of this wire will have a a male 3/16" terminal, to go to the regulator module wire with the small female blade connector.

The second wire has a 1/4" female terminal on the alternator end and a 1/4" male terminal on the other end, which connects to the regulator wire with the large female blade connector.

The third wire should have a suitable sized ring terminal on either end. The alternator end goes to the ground screw, and the regulator end goes to a 8-32 x 1" bolt which passes through the regulator mounting hole. If you can't tell which mounting hole has the internal ground connection, be safe and use two bolts. one through each hole. Connect the wire to both. Secure with star washers and 8-32 nuts. Use heat shrink tubing to insulate all non-grounded regulator connections, and secure the regulator so that it can't cruse around the engine compartment (like maybe to the spot where the old factory generator regulator was mounted).

So, that's it - you now have an externally regulated AL82.

So, why, you ask, did I really do this? Well, my alternator did take a dump, but it was at home, not in the middle of nowhere. And sorting through replacement regulators, i find that the regulation voltage varies wildly. I guess aftermarket stuff just doesn't hold manufacturing tolerance any more. So I said, "Screw this", and am going modify a regulator by adding a trim pot, so the voltage can be set exactly. Obviously, this can't be adjusted with the regulator inside the alternator. So I decided to go external. Now the ideal solution would be to use an AL78 alternator which is designed to use an external regulator, but they seem to be made out of "unobtainium", so that option isn't viable.

Please, don't hit me...
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Last edited by telford dorr on Mon Jan 09, 2017 12:39 am; edited 1 time in total
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busdaddy
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PostPosted: Sun Jan 08, 2017 7:51 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

Very Happy Nice work! Cool not that I'd ever even consider a fix such as this Wink
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PostPosted: Sun Jan 08, 2017 8:29 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

I'm seeing a reality tv show soon on the Velocity channel it's called MacTelford. It's about a genius do gooder that fixes VW buses using bubble gum and paper clips.
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telford dorr
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PostPosted: Sun Jan 08, 2017 8:36 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

aeromech wrote:
I'm seeing a reality tv show soon on the Velocity channel it's called MacTelford. It's about a genius do gooder that fixes VW buses using bubble gum and paper clips.

Seems I spend most of my wrenching time doing just the opposite - fixing busses that were fixed with bubble gum and paper clips. But every once in a while, you just have to go to the dark side...

Or maybe it was from watching that program on car repair in Cuba...
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To steal ideas from one person is plagiarism; to steal from many is research - Steven Wright

In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh

All models are wrong; some are useful - George Box

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PostPosted: Sun Jan 08, 2017 9:05 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

aeromech wrote:
I'm seeing a reality tv show soon on the Velocity channel it's called MacTelford. It's about a genius do gooder that fixes VW buses using bubble gum and paper clips.


MacTelford is one of those amazing people who memorize wiring diagrams for fun and has a sixth sense about anything to do with electrons.
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PostPosted: Mon Jan 09, 2017 4:39 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

so here is a question for MacTelford. I notice he is Scottish and not Irish. Of course he could be an Oe'Telford
Q. Is an electron going forward in time the same an anti-electron going backwards in time?
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PostPosted: Mon Jan 09, 2017 5:40 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

Why stop there? Go ahead and add your modified part to your mobile parts kit ( that everyone should have Cool ) That way, if, in fact, it happens to you way out in the boons, you already have half the job done in kit form.
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telford dorr
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PostPosted: Mon Jan 09, 2017 9:16 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

SGKent wrote:
so here is a question for MacTelford. I notice he is Scottish and not Irish. Of course he could be an Oe'Telford
Q. Is an electron going forward in time the same an anti-electron going backwards in time?

That's a "Is the glass half full or half empty" question. The correct answer is "Neither. The glass is too big".
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All models are wrong; some are useful - George Box

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asiab3
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PostPosted: Thu Jan 11, 2018 1:53 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

Hey dudes,

I have a friend whoís AL82 alternator randomly stops charging. Sometimes at idle, sometimes at freeway speeds. Are we looking at a potential candidate for an external regulator like this thread talks about? Brushes look good, all connections are clean and polished, and the alternator has a good dedicated ground wire.

Thanks!
Robbie
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Starbucket
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PostPosted: Thu Jan 11, 2018 2:27 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

asiab3 wrote:
Hey dudes,

I have a friend whoís AL82 alternator randomly stops charging. Sometimes at idle, sometimes at freeway speeds. Are we looking at a potential candidate for an external regulator like this thread talks about? Brushes look good, all connections are clean and polished, and the alternator has a good dedicated ground wire.

Thanks!
Robbie


Check that the brushes moves freely and spring tension is good. The external reg. sounds like a good idea to keep the internal heat down inside the alt.
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asiab3
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PostPosted: Thu Jan 11, 2018 5:52 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

Thanks Starbucket.

I removed the brush holder, and the wire connections are clean, the brushes are clean but properly broken in, and the brushes move in their housings smoothly under spring tension. There is no binding, but the slip rings look a little worn. Is there a spec for brush length and/or spring tension? Iíve looked in all my manuals, and since itís not technically an original VW part I canít find the specs I want.

At this point, I am going to add Telfordís spade mod to the brush holder so I can hook up an external regulator as necessary.

Robbie
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telford dorr
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PostPosted: Thu Jan 11, 2018 5:58 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

If that doesn't fix it, and if you / he's in the neighborhood, the alternator test stand is over at Gary's place. I'd take it over, spin it up on the stand and take a couple of voltage measurements. If there's still voltage between the rotor brushes when the output stops, then the rotor is suspect (specifically, the wire connections to the slip rings). On the other hand, if both voltages zero at the same time, then bench test the regulator.

Other possibilities:
- regulator connection terminals at the brush holder are loose.
- regulator mounting screws loose, causing a poor ground at the regulator.
- evil spirits.

The regulator contributes insignificant heat, and thus won't affect the cooling air stream. Most heat is from stator winding losses and diode losses.

The main point of the remote regulator is to make diagnosis possible without removing the alternator from the engine (a PITA, for sure), and to allow me to adjust the alternator output voltage as a compensation for the poor QC of the current production of regulator modules.
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'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones

To steal ideas from one person is plagiarism; to steal from many is research - Steven Wright

In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh

All models are wrong; some are useful - George Box

More VW electrical at http://flowcon.us/td/ (available 9am to 9pm PST)
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telford dorr
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PostPosted: Thu Jan 11, 2018 6:16 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

One side note to the brush holder mod: there's not a lot of spare room around the screw that you're adding, so use one with a small head so that it doesn't accidentally ground to the alternator case. An allen head screw would be ideal. You'll want its hole to be as far away from the edge of the brush holder as possible.
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'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones

To steal ideas from one person is plagiarism; to steal from many is research - Steven Wright

In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh

All models are wrong; some are useful - George Box

More VW electrical at http://flowcon.us/td/ (available 9am to 9pm PST)
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PostPosted: Thu Jan 11, 2018 8:54 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

This is my Alternator regulator with current limit. The 3 phase bridge diodes were mounted on a 12" x 7" heat sink, which was mounted on the regulator enclosure. It was in service for 10 years, until I sold my Bus.

Image may have been reduced in size. Click image to view fullscreen.

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PostPosted: Thu Jan 11, 2018 11:08 pm    Post subject: Re: AL82 Alternator Hack Reply with quote

All Tel has to do is whisper and the electrons start to shake and shimmy. 😬
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