Please Help - Alternator Not Charging?

[coolj30]

I am not a newbie with VW's, but I am stumped! Any advice would be much appreciated.

The light bulb in the dash works! So its not that.

I have a 69 convertible Beetle. The Generator light on the dash was on and the generator was not charging.
While running I would unhook the negative battery cable and the engine will die.
I put new brushes in it, replaced the regulator, new battery ground strap and cleaned mating surfaces and battery cables; still would not charge and dash light was on.

I bought a brand new alternator, installed that and removed the regulator.
Still will not charge! And red G light is still on.
I checked continuity from alternator wiring to battery. All good.

What am I doing wrong!?

[SCOTTRODS]

Year model not important... Please clarify if you're using an alternator, or a generator... and if alternator, give more specifics of any updates done... wiring changes etc...

[Marc]

I'll assume you got an internally-regulated alternator (two wires).

Check your work against this guide: http://www.speedyjim.net/schem/gen_alt.htm
...hopefully you'll find the problem there and won't need to go further, but if not read on before you do.

The fact that you could lift the negative battery cable and the engine would die does seem to indicate that the generator wasn't working but it's not conclusive since at idle speed it might not be charging (there's a cutout circuit in the voltage regulator that releases the generator when the RPM goes below a certain point - that keeps it from trying to act as a motor when the engine's off which'd drain the battery.) DO NOT make that particular test with an alternator, they need the battery in the circuit to provide a reference and without it can "run away" making excess voltage and causing damage.

The warning light merely compares the voltage available to one side of it (from the battery to the lighting switch to the ignition switch to the shell of the lamp) with the voltage available to the other from the alternator's small D+ terminal. If there's more than a few volts difference in either direction it'll start to glow. That means that the generator/alternator can be working fine yet the light may come on if there's resistance somewhere in the path for the reference voltage coming from the battery. On a `69 Beetle there's no fuse to the idiot lights, just a small-gauge black wire going to their lampholder block from the "hot" side of the second fuse.

If you have a voltmeter, check between ground and the big B+ terminal on the alternator - with the engine off, that will show battery voltage (~12V, never over 13.2).
With the engine running it should go up to 14.2 to 14.7V. Slightly less is acceptable, but anything under 13.2 can't charge the battery at all. You may need to rev the engine up a bit before the alternator kicks in, but after that it should continue to charge at idle speed.

[coolj30]

I am not a newbie with VW's, but I am stumped! Any advice would be much appreciated.
The light bulb in the dash works! So its not that.

I have a 69 convertible Beetle. The Generator light on the dash was on and the generator was not charging.
While running I would unhook the negative battery cable and the engine will die.
I put new brushes in it, replaced the regulator, new battery ground strap and cleaned mating surfaces and battery cables; still would not charge and dash light was on.

I then bought a brand new alternator, installed new 75 amp alternator, and removed the regulator.
Still will not charge! And red G light is still on.
I checked continuity from alternator wiring to battery. All good.

What am I doing wrong!?

[coolj30]

Currently running a brand new 75 amp alternator.
Removed regulator and spliced all large red wires together.

[Marc]

Currently running a brand new 75 amp alternator.
Removed regulator and spliced all large red wires together.

And? What did you do for the D+ wire to the warning light?

The stock "generator" wiring is adequate for a 50 or 55A alternator but for a 75A it's marginal at best. This shouldn't be the cause of the symptom reported, but it needs attention nonetheless. Easiest fix is to add a second 10 gauge B+ wire from the alternator to the battery cable stud on the starter solenoid; be sure it's routed where it won't get chafed. You can use the existing backup light hole in the front tin but make sure the grommet's in good shape; since that wire is "hot" 24/7 you don't want it shorting out.

[coolj30]

I used a spade splice connector and hooked it to the wire going to the front of the car (warning light wire).

I ordered a 55 amp, but they sent me a 75 amp...

[Marc]

I used a spade splice connector and hooked it to the wire going to the front of the car (warning light wire)...

That should be good, along with bonding the three big red wires together. Nothing else to do when converting to an internally-regulated alternator.

Since this problem started when you still had the generator, go over the basics. Battery post connections, neg battery cable where it bolts to the pan, and the ground strap that goes around the front transmission mount.
If the latter is loose/broken you can still have enough of a ground through the clutch cable for the car to start & run. Just check that everything looks clean & tight to rule out a resistance problem in the battery circuit.

Are the oil pressure warning light and t'signal indicator light working normally?

I understand that the charging warning lamp is on with the engine running. Is it also on with the engine stopped and the key in the "on" position? Stock warning lamp, hasn't been changed to an LED?

[coolj30]

All battery connections are good. I removed everything and sanded everything clean.
Terminals and cable mating surfaces.
Oil light and turn signal lights work fine.
Red G light is on constantly. As soon as you turn the key and while running and not running.
No led lights.

[Marc]

It is starting to look as though the new alternator may have a problem, you may need to pull it and take it to your F.L.A.P.S. for testing.

Humor me and confirm that the charging warning light will go out with the key on if you unplug the D+ wire at the alternator.

How high have you taken the engine RPM so far? It can sometimes take a moment at ~2500+ for the alternator field to establish, especially when it hasn't been in use for a long time.

[coolj30]

Key on. Both red dash lights on. Unhooked D+ wire at alternator (smaller wire) Both lights stay on.

Most I have driven it with new alternator was around a parking lot. So it has not seen a lot of high RPM yet.
But I think it is another problem? Because the same thing was happening with the original generator.

[Marc]

Key on. Both red dash lights on. Unhooked D+ wire at alternator (smaller wire) Both lights stay on....

With the D+ wire disconnected at the alternator (and not touching anything) the warning light should be OUT. It'll have voltage to the shell of the bulb coming from the ignition switch but no complete current path.

If the light is on with the wire disconnected, something's providing a path to ground for the warning lamp "signal" wire. Try disconnecting the splice you made when you removed the generator regulator; if the light is still on there's a problem between there and the lamp (and that's just a straight run of wire in the main harness). If it goes out, looks like we're back to rechecking your work or the wire from under the seat to the engine compartment's grounding out somewhere.

Did you do any work on the ignition system lately that involved touching the wires going to the coil?

[coolj30]

Found the problem!.....Maybe.
I took the wire off the alternator and put a voltmeter on the terminal while the engine is running and the alternator is putting out zero volts.
So my brand new alternator is bad.

I am going to remove it from the engine and have it tested more professional.

[Marc]

...I am going to remove it from the engine and have it tested more professional.

But you said that the warning light stays on when the D+ wire is lifted - that's not right, and since that's the current path for the field excitation that circuit must be healthy for the alternator to work.
Before yanking the alternator I'd try one more test - leave the D+ wire off, and connect a test lamp from Term 15 (+) on the ignition coil to the D+ terminal on the alternator. It should come on with the key. You could also go ahead and connect your voltmeter between the B+ post and ground at this time, but it's not vital for the test. Start the engine and observe the light; if it doesn't go out immediately, rev the engine up some (could take a moment at 3000+ RPM). If the light goes out, the alternator's working and you need to focus on the wiring. If not, get the alternator tested.

Even if the alternator is found defective, that still doesn't explain why the warning light is on with the D+ wire detached - it would be an open circuit unless that wire is grounded or crossed with another on its way to the warning lamp.

[coolj30]

Warning light is on all the time. With either wire removed from alternator, light is still on.

I will try your new recommended test. Thanks!!!