Alternator Talk

[Smokey Eddy]

There is something amiss with my charging system now. Almost got stranded about 60 clicks from my place because the car started to slowly die.

I just changed the belt on the alternator so im going to re-tighten it as it probably has slackened a bit BUT i've been wondering:

Is it better to just change the brushes and voltage regulator on the mk2 style units or is it wise to change the whole thing?
I recently replaced the voltage regulator (last year) and am wondering if a $10 brush assembly will fix my issue instead of the other $130 option.
I realize there are bearings in there too but i've yet to take mine apart. Can anyone enlighten those equally ignorant as my self?

All and any relevant input is welcome!

looking at these items:

Ebay Item + shipping
BestPriceCarParts.ca Alternator Free Shipping (over $85)
BestPriceCarParts.ca Brush Assembly The shipping of which to me would be around $11
$54 pulley?

[theman53]

Brushes are cheap and not much loss if it doesn't work out.

If you have the 1.9 now can't you run the serp If you have to change alts now would be the time to do the serp setup.

[lloydbiker]

If you've got the alt out, spin it by hand, to see if the bearings are smooth and quiet. The biggest killer of alt bearings is excessive belt tension. If the bearings feel and sound OK, just replace the brushes, they're cheap and really the only wear item (then possibly the reg too, if it's interal). Those two items account for probably 99.99% of alternator failures. Alternators are pretty much self protecting, so very seldom do they suffer winding or diode failures.
  If your regulator is external, check at the 'F' (smaller) terminal of your alternator, to see if you have battery voltage when the key is on, if not, the reg. is faulty. But, for the price, I would replace the brushes anyway, as you'll eventually have to.
 If you're running the standard timing gear/key setup, and not the TDI type, stay away from serp belts. The only real advantage to them is auto tensioning (when it works).
When you put it back in, be careful not to over-tension the belt.
 You say your car started to slowly die, do you mean engine, or everything else? The diesel should continue to run fine, as long as you have sufficient voltage to hold the fuel solenoid operated. I've limped gas cars and motorcycles home 100s of miles, with NO charging system, and they need power to fire.

[Dakotakid]

^^ what llyod sez.

It is easy to replace the brushes with a soldering gun and maybe just a little additional solder needed to reattach. Make sure you catch the little springs when you melt the brushes (one-by-one) loose. You will need those on your new wire.

Also, inspect your slip rings (surface which the brushes ride on) to see if their surface is still smooth and flat. If the surfaces are irregular, you can do a "hillbilly smoothing job" with your finger and some fine crocus cloth. In other words, with the regulator removed and the belt off or very loose, insert your finger and lightly press the abrasive surface against the slip rings while turning the pulley (shaft) by hand. Remove as little of the surface as possible. Blow out the dust with air when done. The brushes need a smooth surface to last long and this manner of smoothing them out has lenghtened the life of my alternators a great deal.

Be very careful when reinserting the regulator to get those brushes in the correct position. It's kind of a rotate-push thing.

[Quantum TD]

Does your battery light come on when you turn the key to accessory? If so, then check the brushes/voltage regulator. If not, your diodes may be bad. When the diodes die, they trigger the battery light on the dash when the car is running. But, if your battery light LED is burned out, then you wouldn't know if the light stays on when the car is running. Diodes are internal to the alternator IIRC, and you will need to replace the alternator.

[lloydbiker]

I just took a closer look at the picture of the brush assembly. Isn't that brushes, holder and regulator too?
If so, you may find the problem to be just a loose mounting/grounding screw on the assembly. IIRC the ground for the regulator and for the rotor, is one of the assembly mounting screws.
As such, if it's loose, you'll get no or at best intermittant output because the rotor can't energize properly.
At $10, the unit is about 10% of list cost, and about a 99% rebuild. Buy one just so you'll have it if needed, down the road. I have to assume you don't have a tach, if you're considering a rebuilt without a 'W' lead.
A lit battery LED when running, only indicates no output,because all they do is light on reverse flow (from battery TO alternator) which could be from any of the mentioned causes.
BTW, LEDs are generally rated at 100,000 hrs, so don't often fail. That's why they're used for indicators now, rather than bulbs, which, if you're lucky, have a 1,000hr life rating, and are usually a *** to replace. The circuitry is also simpler with the LED indicator.
I say again, DON'T OVER-TIGHTEN THE BELT or you will be doing a complete rebuild later.  


AAA  A lot of the brush holders also have a hole for insertion of a paper clip, or some such, to hold the brushes retracted for insertion. Then, you pull it out to release the brushes.



[

[Quantum TD]

BTW, LEDs are generally rated at 100,000 hrs, so don't often fail. That's why they're used for indicators now, rather than bulbs.    

I've seen several burned out LEDs on VW dash clusters in my life. Not common, but it does happen.

[Smokey Eddy]

Wow thanks everyone. The belt was loose but I've suspected worn brushes for quite some time. My stereo dims the lights quite badly. What gave me grief last night was that it was pouring rain and a busy highway. So my lights were dim, wipers slow, no defogging and so on.
I will buy brushes then as it sounds like the diodes are fine. I'll also smooth the mating surfaces.

[lloydbiker]

But the engine ran just fine, right?  Again I say DON'T OVER-TIGHTEN THE BELT! Better to have to re-adjust often, than to take out the bearings.
One of the ferrying trips I made by motorcycle, without a charging system, was 5 hours, on the highway, with no brake lights or turn signals. Thank God my wife knew exactly what I would do in a given situation. She followed tight behind, on her bike, as my signals. Another trip, we brought her car home 50 miles, in the dark, with no lights other than brake lights, her following me in the truck. Some of my friends have brought bikes home over a thousand miles with no charging system, just kill everything not necessary to get down the road.  

[lloydbiker]

Here's a little tidbit of info:
Application Notice B-85
1985-90 Volkswagen Golfs, Passats and Jettas may exhibit low alternator output, alternator charge light on, or squealing belts when driven in wet conditions. To correct this condition, Volkswagen has released splash sheilds to be installed over the drive belts to protect them from moisture and prevent the belts from slipping which causes the low alternator output and squealing belts. Splash shield #191 0250 01C should be used for Golfs and Jettas, and #357 825 254 for Passats
Of course this applies only to V-belt equipped cars, so it's +1 for the serp belts, after how many -?
Found using Google search.

[Smokey Eddy]

Oh cool ill try and find that cover.

[Vincent Waldon]

If you find more than one you can probably get rich reselling it...the general belief is that they are NLA, except in junkyards.   

[damac]

How do you tell if your belt is too tight on these?

My jetta has no power steering or ac.  I put a new belt on and used a screwdriver to pry a bit.  Car runs without the belt bounching.

But when I go under the car I noticed that I can grab the water pump pulley with 2 hands and pretty easily turn it, so it made me think the belt isn't tight.

The water pump seems to return based on throttle to the reservoir when I reve it up, and the car hasn't gone past mid temps no matter how its driven either.

[lloydbiker]

According to my old Bentley, you should be able to depress the top run of the belt 1/8" to 1/4" at mid-span without excessive pressure.
Re: Here's a little tidbit of info:
I just found it interesting that Bosch still shows that reference in their catalog, although, as was said, the part is long since NLA.
Also, I did find a little alternator trouble shooting chart in my old Bentley.
It says: Ignition off, warning light on. Disconnect plug at alt. If light goes out: faulty diodes. If light stays on, short in wiring or connector. So, there is a simple test for shorted Diodes, but not really for 'open' ones