Battery not charging

[unclegreen2]

Hello folks, I have a 71 super beetle. I had a new battery installed about three months ago. I've noticed the red light coming on even at high idle. I drove the car a few miles and parked in my drive. When I went back to restart my car the battery was dead. I jumped it with a portable jumper and it started right up. As I said I have seen the red light coming on even at high idle Thanks for your input

[Brian]

Hi and welcome to the forums

Sounds like its definitely something with your gen/alt. What do you have in the car right now? A generator or an alternator?
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[unclegreen2]

I don't know how to tell Thanks for your reply

[Cusser]

[unclegreen2]

I don't know how to tell Thanks for your reply

[unclegreen2]

I don't know how to tell Thanks for your reply

[unclegreen2]

judging by the photos looks like an alternator

[74 Thing]

Is the red light on all of the time and is it an internally regulated alternator like in the photo?

If so there are three wires to the alternator: 1. Red one goes to the battery; 2. There is a ground wire that screws to the body of the alternator; 3. There is the warning light wire that is a spaded connector and runs to your dash light.

All wires need to be hooked up so that the battery charges properly. Get your voltmeter out and start checking to see if it is charging property at the alternator (eg red probe to the battery wire terminal and black probe to the alternator body for the ground). While the engine is running it should be 13+ volts and may go up a bit when you rev.

[ashman40]

Post a pic of your engine specifically around the generator/alternator wiring and we can confirm which you have.

Here's a pic of the different charging units that VW has used over the years.

Generators are "cylinders" with an even diameter over the entire length.
Alternators have a narrow body near the fan shroud which then transitions to a larger diameter body at the fan belt end.

All generators have an external regulator (usually located under the rear seat) with three wires (D+, D-, DF) running between the regulator and the generator (one thick and two thin). The regulator has an additional two wire terminals (B+ and #61).

If you have an alternator, there are two types:

externally regulated
internally regulated

The internally regulated models have a single thick wire (B+) and a single thin wire (D+).
The externally regulated models have a single thick wire (B+) and three thin wires (D+, D-, DF) that run to the external voltage regulator (VR).
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AshMan40
---------------------------
'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[unclegreen2]

Thanks for the photos that definitely helped. Its a bosch AL829n alternator.
The red light is not always on. Just when idling and even then its only on some of the time . But the engine seems to be idling fast enough that the light should be out.

[VW_Jimbo]

Sounds like a loose belt. Have you checked it?
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Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[unclegreen2]

How much play should there be in the belt because there is a bit. Sounds like a good place to start. How is the belt tightened?

[VW_Jimbo]

Man, I do it by feel. I would guess about 5/8 inch of play, measured at the midpoint of the belt, between the pulleys. Push it in with your finger, towards the interior area of the circle of the belt. Hope that makes sense.

Do you have a manual of any kind? I know it would be in there, with pictures and better writing than I can produce!

Belt gets adjusted by adding or removing shims from between generator pully halves. The extra shims are placed onto the shaft between the nut and the pulley.

Edit - here is a link to Rob and Dave's page on adjusting the belt. Great write up.
http://www.vw-resource.com/fanbelt.html
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[unclegreen2]

I just checked the tension on the belt. It seems to be just right at 5/8 of an inch play when belt is pushed inward at center.

[VW_Jimbo]

If the belt play is good....then you need to check voltage at different points in the cycle. Do you have a volt meter? Do you know how to use one?
_________________
Jimbo

There is never enough time to do it right the first time, but all the time necessary the second time!

[unclegreen2]

Yes I have a volt meter and I do know how to use it.
I will check voltage between battery terminals before engine is started and compare the reading after I start the engine.
Where else should I check?

[unclegreen2]

I checked the voltage between terminals before starting it was 11.88 volts.
I tried to start the car but it wouldn't start.
I jumped the car with a portable jumper. I then took a reading between the battery terminals while the car was idling high it read about 12.25 volts.

I shut the car down and tried to start it again. It barely started. I had my wife rev the engine and hold it there. When I took the reading this time it read below 12 volts.

So the battery isnt getting charged. Does this mean the alternetor is bad or could it be something else?

[Cusser]

[JuggButt]

Try replacing the voltage regulator. I had a remanufactured one from NAPA that had lasted for several years and then it failed. I ordered a couple remanufaactured ones on the Internet and they were both bad. I finally spent the extra money and bought a solid state Bosch and never had the problem again. But I should have done that before replacing the generator.
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[ashman40]