Slow but steady progress...electrical stuff (i hate it!)

[vwfye]

I have a continual charge light on the dash of the 412. so, i started with the basics (less my meter as it is still packed from the move). i replaced a suspect/corroded postive terminal on the cable. checked the tranny ground and the negative ground on the battery to body. pulled the VR for a new one and no change. So, I guess it is time to pull the alternator.

Do I understand correctly that it is easier to drop the exhaust to remove the alt than trying to work around it? Also, is this a rebuildable unit for a novice?

[raygreenwood]

I don't think the alternator is any easier or harder than any other. Generally, I think the lack of bearings, diodes, slip rings etc....available to work with this alternator, may discourage you.
These are very high quality builds. I have yet to have one last less than 250K miles.
Before taking the alternator out....other things to check.
Check the ground strap at the nose cone of the transmission. Check the T-1 connectors (black, gray and blue) near the VR. Check the large red and white wire that goes into the alternator loom for corrosion.

Also....check the light in the dash itself. It may be a ground issue. Also...do you mean the light on the right hand instrument...or the light on the "B" indicator between the instruments. Generally...though that is for brakes, on some early models....it also would light up with the alt. light as the ground failed to the instrument panel. Ray

[vwfye]

i have already checked the ground straps, the red/white wire and it is the correct dash light.
the car sat for 10 years and who knows what has crawled inside the alternator in that time. all i know is the dash light won't go out (battery shape inside the right gauge) and the battery gets drained from the vehicle running.

[MGVWfan]

Given that you've replaced the regulator (assuming the new one is good), the only way for the alt lamp to stay lit when running is either something's grounding it (pull the connector to the regulator to break the field's ground, turn on the ignition, and the lamp should not light if all is well with the lamp circuit), or for the alternator to have a bad field circuit (brushes, slip rings, field winding, wiring), ground diode set, or exciter diode trio. Too bad.

It's a Bosch AL75X rebuilt...here's one source...

https://pointer.webappcabaret.net/busde ... dgroup=595

Can't beat $99 for a real Bosch rebuilt, even the falls-apart-on-the-way-home auto parts chain cheapies are something like $50 around here.

Both bearings were toast on mine, but the brushes, etc. were OK, so I replaced the bearings and pressed on. Ray's correct, it's impossible to find brushes and diodes without a friend in the auto electrical rebuilding business...and even then, the price for a set of diodes exceeds the price of a rebuilt alternator. The brushes were something like $40 for a pair, outrageous.

[DeathBus]

You can work around it, but removing the exhaust and heater boxes will give you an opportunity to clean up rusted or worn out mating surfaces. Exhaust leaks will kill your engine.

[MGVWfan]

I've been told a long flat file used carefully is good for dressing up the exhaust manifold flange tops...sounds right to me. DB/Ray?

[DeathBus]

I've been told a long flat file used carefully is good for dressing up the exhaust manifold flange tops...sounds right to me. DB/Ray?

Yes use a blue MARKS ALOT and color the flanges, use the bastard file until all the blue is gone and your flange is nice and level again.

[MGVWfan]

Hey, that's my old trick, using Redneck Blue (Marks-A-Lot) like that! Cheaper than Prussian Blue, eh?

[DeathBus]

Hey, that's my old trick, using Redneck Blue (Marks-A-Lot) like that! Cheaper than Prussian Blue, eh?

Well I am in Alabama

[vwfye]

well, color me lucky! a buddy i have told me he has an alternator for me. Shipped for 15 bucks! whoohoo....

oh, and my exhaust has no leaks! so, as long as i am careful, i should have the car running early next week.

[albert]

allo, vwfye, it is not necessaire to reemove the heather box for joint the alt. only the muffler and steel cover plate very fast , ,,albert

[vwfye]

update... and frustration!

Upon vehicle start, the voltage at the battery climbs to just over 13v... but, the charge light doesn't go out and the battery discharges as the vehicle runs... the battery checks out as good, but i am having my suspisions. if the charging system is functioning but the battery has an issue, would this cause the charging light to stay on? it seems like (to my simple mind) that if the circuit is complete, the circuit is compete and the light should go out.

as stated before, i checked grounding straps at ground, replaced a corroded cable, inserted a NEW vr into the mix and next is an alternator if need be.

[DeathBus]

The alternator is bad

[vwfye]

what would explain the Voltage gain after start up? i'm not doubting you... just trying to learn something as i go...

[MGVWfan]

Concur.

Long answer...
The charge lamp staying lit tells you that one side of the lamp has +12V from the battery, and the other side is grounded through the field and regulator, indicating the exciter diode trio isn't producing any juice for whatever reason. All the reasons why the trio isn't providing juice mean an alternator pull and replacement (bad trio, bad negative rectifier diodes, bad field winding, bad slip rings, bad brushes).