Alternator warning light question

[socal1904]

Let me start if by wishing all the Dads a great Fathers Day.

I was not aware the alternator light needed to be in working order for the alternator to charge the battery, needless to say my battery eventually died. I replaced the bulb, jumped started the car, but now the light will not go out. Is this due to the dead battery and once it charges back up it will go out? Or could it be the alternator itself is bad. Have some checks to do, but was hoping for a heads up in he right direction.

Thanks.

[Cusser]

An alternator is not really designed to charge a "dead" battery, wonder if that is the reason...

Yes, an alternator needs that warning light to be operative to charge.

What's the voltage across the battery terminals when running engine at 2000 rpm?
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[socal1904]

Been meaning to get a voltmeter, guess I know have no excuse. The wiring seems to all check out, gonna try to get the battery charged and see if the light will go out, unfortunately it’ll have to wait.

[Cusser]

[socal1904]

Have not had a chance to go get a voltmeter but did jumpstart the car, let it idle and reved it on and off for some time and then went for a short drive. The alternator light remained on while idling but would go dim and then go out completely while driving, but then come back on again while idling. Hoping that once I get the battery fully charged the light will stay off.

[socal1904]

Okay, I now it’s been a while but here’s an update. Got the battery charged overnight at AutoZone and got a voltmeter. The battery registers at 12.6, I turn the car on and it remains the same, goes up slightly, between 12.9 and 13.1 at idle. When I rev the engine it does go up to the mid 14’s and if I rev it higher it went up to the mid 15’s. Is the alternator toast? On its way out? Could it be just the voyage regulator? Can the internal ones be changed out?
Thanks in advance for any info!

[socal1904]

Oh and the light stays on unless I take out for a drive, then it dims and goes out under load but comes back on at idle.

[Cusser]

Sounds like you need a new alternator, unless the internal regulator can be replaced.
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[Danwvw]

Alternators tend to wear down one brush, You can probably find one at the hardware store that will fit.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!

[empi3]

If it turns out to be your regulator, you might be able to replace it with this.

https://www2.cip1.com/ProductDetails.asp?ProductCode=VWC%2D043%2D903%2D803%2DF

VWC-043-903-803-F - GERMAN MADE - VOLTAGE REGULATOR - INTERNAL FOR GENUINE BOSCH ALTERNATOR - BEETLE 71-79 / GHIA 71-74 / BUS 1971 / THING 73-74 - SOLD EACH

Steven
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The fact someone posts a thousand messages a month does not mean the messages contain anything worth reading.
Bob Hoover

1970 Beetle
1956 Ragtop Beetle

[socal1904]

Does anyone have a write-up / How-to on the process, been sifting through the search results but have had no luck.

[mukluk]

[socal1904]

Replacement of the internal voltage regulator.

[mukluk]

The info and pictures in this thread should give you an idea:
https://www.thesamba.com/vw/forum/viewtopic.php?t=599274
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1960 Ragtop w/Semaphores "Inga"

[Danwvw]

Ok, So next question. What kind and model number is your Alternator. For Example, it could be from a 1974 bug which was made by Motorola and used an external Voltage regulator, There were a couple of models of them. One with the reg on outside of the Alternator and the other the Reg was under the back seat. Or it could be a Bosch AL82N which uses this. Here is a link: for it: replacing internal regulator on Bosch AL-82N. That I found by Googling "Bosch AL82N alternator regulator" and selecting images and looking at pictures for it.
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1960 Beetle And 1679cc DP W-100 & Dual Zeniths!