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Mon Aug 28, 2023 8:26 am

Hi all, figured I’d post in this forum because it’s not a Type 3-specific question and this forum is a bit more active.

Lately my 6 volt generator brushes have been wearing out really fast. I’ll go through a set in about 1,000 miles.

Previously, using this same generator, the brushes would last more than 6,000 miles.

I’m using the ones that Wolfsburg West sells, they are labeled with the brand name Schunk.

Just posting to see if anybody else is having this kind of problem with these brushes or has any insights as to why this happening. Charging system works fine otherwise.

After the last set wore out, I removed the generator and disassembled it to clean and polish the commutator but the new set of brushes wore out just as fast.

Mon Aug 28, 2023 8:39 am

Did you undercut the insulation after turning it?

Mon Aug 28, 2023 8:57 am

Hi Phil, thanks for the reply. I didn’t have the commutator turned on a lathe, I just pulled out the armature for better access and used gasoline to get the carbon residue off the commutator and then a fine polishing cloth to brighten it up as described in the Bentley. This generator was completely overhauled about 6 years ago but I don’t know if I should expect commutator issues to crop up within that time frame?

At least it’s easy to remove/install the generator in a Type 3 😊

Mon Aug 28, 2023 11:10 am

sjbartnik wrote: Hi Phil, thanks for the reply. I didn’t have the commutator turned on a lathe, I just pulled out the armature for better access and used gasoline to get the carbon residue off the commutator and then a fine polishing cloth to brighten it up as described in the Bentley.

Was the fine polishing cloth abrasive?

Using abrasive (emery) will embed into the commutator turning it into a grinding wheel.

Saw this on many motorcycle starter motors over the years.

Mon Aug 28, 2023 3:31 pm

No, nothing like that. It was a fine metal polishing cloth meant for things like jewelry. I didn't want to use anything that might embed abrasive particles into the copper.

Mon Aug 28, 2023 3:47 pm

sjbartnik wrote: No, nothing like that. It was a fine metal polishing cloth meant for things like jewelry. I didn't want to use anything that might embed abrasive particles into the copper.

Based on that I would have to guess it is poor quality brush material.

Just one more example of deteriorating quality of parts.

Mon Aug 28, 2023 3:49 pm

What shape are the brush springs in? Too tight or too loose can cause wearout. How do the brushed and commutator look when worn? Black, shiny, ??

Mon Aug 28, 2023 4:21 pm

The springs seem fine, 100% stock as far as I can tell. There is definitely some black carbon residue deposited on the commutator where the brushes ride.

I have noticed that the bottom brush tends to wear out first which is when the generator light starts to flicker at speed. That will happen when the bottom brush gets to be about flush with its holder while the top brush will still have a bit of brush extending above the holder at that point.

Also when I removed the brushes this past weekend, the bottom brush had what appeared to be evidence of arcing. [EDIT: not evidence of arcing, it was just carbon dust buildup on the edge of the brush - my bad].

Tue Aug 29, 2023 10:31 am

markendee wrote:
Based on that I would have to guess it is poor quality brush material.

Just one more example of deteriorating quality of parts.

I don't know if I'm ready to concur with that yet. Wolfsburg West generally sells quality parts and researching Schunk online they appear to be a major German manufacturer of carbon brushes for all sorts of applications from, as they say, household appliances to wind turbines.

https://www.schunk-group.com/carbon-technology/en/products/carbon-brushes

I'm starting to think it's more likely that perhaps my commutator has worn out of round and brush life is suffering as a result.

I would expect 6v brushes not to last as long as 12v brushes because they are dealing with higher current levels and also because they are smaller than the 12v brushes, but these are definitely wearing way too fast.

Tue Aug 29, 2023 2:31 pm

When you spin the generator by hand do the brushes shift up and down?

One thought... if the regulator is forcing the generator to work harder by overcharging the battery, that can cause brushes to wear out quicker.

Tue Aug 29, 2023 5:20 pm

glutamodo wrote: When you spin the generator by hand do the brushes shift up and down?

Good question, I'll check.

Quote:
One thought... if the regulator is forcing the generator to work harder by overcharging the battery, that can cause brushes to wear out quicker.

I haven't seen any reason to suspect the regulator. A few years ago (2016) I had an electronic regulator built for me by Clover Systems and it's been working flawlessly ever since and continues to do so as far as I can tell by basic electrical testing.

For some additional info, this latest brush wear-out happened during a 200 mile road trip. When I was almost at the destination, I began to see an occasional flicker of the generator light, and I knew that probably meant my brushes were on the way out again. I continued on to my destination. While there, I checked the brushes and they were worn out. I put on a set of spare brushes I had with me. Based on my records I had gotten ~1200 miles out of that set.

By the end of my return trip, which was 200 miles of night driving (lights on), the brand new brushes were totally worn down - bottom brush flush with its holder, top brush barely protruding. So something is obviously wrong to wear a set down that far in 200 miles.

Wed Aug 30, 2023 7:32 am

Okay, good, it's a solid state regulator, so you can rule that one out.

Wed Aug 30, 2023 7:40 am

I have a spare generator that I’ve swapped in for the time being, so I will take the brush-eating one apart and see if I can find anything obviously wrong with it mechanically or electrically. Will post findings as I go in case it may help someone in the future.

Wed Aug 30, 2023 8:42 am

Post some pics of the commutator and the worn brushes. Maybe something will jump out.

Wed Aug 30, 2023 3:08 pm

Will do, should be able to re-visit this in a week or two.

Fri Oct 13, 2023 11:28 am

Having the same problem, I just replaced my brushes Aug 7 and the light came on 2 days ago. If I push down on the top brush the light goes off so I think it is definitely the brushes but 3 months is way too fast to be worn out. Springs are exactly how they were when I replaced them so I don’t think they’re too tight but I also don’t actually know how to loosen them. I got the brushes from Jbugs. I don’t want to just order the Wolfsburg West brushes and have them go out in 3 months too. Any thoughts?

Fri Oct 13, 2023 3:22 pm

Is the brush worn down below the top of the holder slot?

Did you clean up the commutator when changing the brushes?

Is this using an old style electro-mechanical regulator or a modern solid state?

Fri Oct 13, 2023 9:07 pm

I didn’t clean the commutator it looked pretty clean. The brushes are definitely worn down below the top of the holder slot, and they’re worn evenly, the top and bottom brush are both below the top of the holder slot. It’s the standard regulator I believe. I haven’t replaced it since acquiring the car in 2003.

Sat Oct 14, 2023 11:10 am

I’m going out on a limb but it sounds like low quality brushes. It’s expected, but not welcome, to happen with most VW aftermarket parts now. You’d be able to feel a high or rough spot on the commutator were it the problem.

See if you can find an old generator locally that you can rob brushes from. Most people don’t seem to want generators any more so they are generally available and not that expensive used

Sat Oct 14, 2023 12:17 pm

I have a few ideas, but no good answers.

1. Try turning the generator by hand with the tip of a sharp pencil riding the armature at about a 45 degree angle. Feel for high spots or roughness. A smooth run suggests the armature is smooth, but is not proof. One cause of rough armatures is a loose bar that only lifts under centrifugal force.

2. I suggest taking a medium or fine brush stone to the commutator while the engine is running. You should pull the brushes and disconnect the regulator then gently run that stone back and forth across the brushes until they are smooth and bright copper colored. These can remove a lot of material, keep it light and no longer than needed to clean up the commutator.

3. The dark chocolate color the commutator develops where the brushes run is a good thing. As new brushes seat in it will return and you don't want to unnecessarily disturb it. Brushes wear faster until that patina develops.