Car not charging, no battery light on dash, no exciter?

Finding good information on this has been a huge pain.

My battery light isn't coming on when I switch the key to run before starting, or when the engine is running (and the alternator is NOT putting out voltage, since it never puts out voltage).

Alternator is "Fresh", probably rebuilt, alternator from the parts store a few days ago. I put that in because I didn't have 12V at the + post on the alternator itself. It didn't help.

Here's what I've checked

Battery voltage (after charging with external charger) 12.8V
Battery voltage after starting, lower and will continue to drain as the car runs.
Checked resistance from alternator (power) cable to battery fuse block. Good.
Fuse block on top of battery is in perfect condition.
Cleaned both grounds under battery tray. They're both good, I get 0 Ohms between the - terminal and either ground. 0.2 - 0.3 ohms to the block and alternator case.
Checked power at the connector above the starter and at the alternator. Orange (not sure about the stripe) has voltage. It was 11.7v last night but the battery was also a little drained at the time.
Checked for chafed wires, grounds, etc in the harness below the battery box.

My questions are;

How do I test the battery light on the dash?
I tried to jump the 2 wires at the alternator and at the connector above the starter, nothing.
Tried grounding either wire, nothing.
Tried +12 to the non-electrified wire. Nothing.
Should both of those wires read +12v to ground? This post says I should

I put +12v to the alternator connector and still didn't get 14V at the battery.

I'm stumped.

Does anyone have a diagram that explains the battery light wiring?

Of the 2 wires in the small connector on the alternator, the +12v wire comes from where? (I assume mine is fine because I have +12v)
Where does the other wire go?

This post has me thinking I should put +12V to the wire that doesn't have voltage. I have +12V on the orange/brown wire (closer to the engine block I think)

Just finished reading this whole thread. I'm thinking my issue with the blue wire. It tests good to the harness above the starter. I have no idea where to test after that as it goes into the car.

What else am I missing here?

Those alternators you buy from parts stores have a life time warranty. Take it back get another. You have a bad one. If its not kicking out 13.8-14.3 or so on the stud on the back of the alternator, with the engine running, it's a bad rebuild.

I just went through this with an Autozone reman starter. Changed it out twice, finally bought a Bosch.

The problem with changing out the alternator over and over is the location on the ALH engine. That's why a Bosch is so highly recommended.

I agree with Tdijarhead, I've gotten bad rebuilt starters and alternators from local parts stores numerous times. Get a Bosch remanufactured from one of the vendors here on the club.
Don't forget to check if the clutched alternator pulley is working correctly.

pudman2003 said:

Don't forget to check if the clutched alternator pulley is working correctly.

Click to expand...

I did, the clutching is good.

I haven't yet had my old one tested because I was hoping to get my money back for the new one via "warranty". Perhaps I'll have them test that one. I have some faith, but not a ton, in my local parts store. This would be the first time I got something DOA from them. And with 537k on my car, I've bought a lot of stuff.

Parts store remans are just plain junk for the most part. Not only for VW, but across the board. I had a friend that owned a NAPAparts store and he would test the alternators and starters that he got for restocking the shelves before he put them on the shelf. 40% of them got sent back without being sold over the counter.

given the choice of a parts store reman, or a good used one from the wrecking yard, i will take a used one every time. i have better things to do than endlessly changing alternators or starters. We don't purchase crappy remans, but we have had a few "carry ins" that we have had to do twice, or thrice.

Does the charge light come on with the key? There is a fuse for the charge light circuit. #11, 5A underdash. There is also a huge fuse in the fuse panel for the charge lead to (from) the alternator in the underhood panel. 150A. Mitchell calls it fuse 5. You said there was no voltage at the alternator post. it should be battery voltage at any time running or not unless disconnected somehow. (blown fuse)

Might check the ground to top of transmission.
You should see a bump in volts when the car runs.
Starter wire- did you check continuity or resistance? R=size x length. They sometimes get corroded inside.
Battery must be load tested or specific gravities checked (no one does this anymore).
But it does just sound like alternator.
There is tons of info out there to troubleshoot, this is not a vehicle specific system.
Try this for forum search, all forum search engines are poor-
VW TDI Search Engine

pdq import repair said:

Does the charge light come on with the key? There is a fuse for the charge light circuit. #11, 5A underdash. There is also a huge fuse in the fuse panel for the charge lead to (from) the alternator in the underhood panel. 150A. Mitchell calls it fuse 5. You said there was no voltage at the alternator post. it should be battery voltage at any time running or not unless disconnected somehow. (blown fuse)

Click to expand...

No the charging light / battery light does not come on with the key.


I know I need to fix this before I can start going down the road of a second bad alternator.

BobnOH said:

Might check the ground to top of transmission.
You should see a bump in volts when the car runs.
Starter wire- did you check continuity or resistance? R=size x length. They sometimes get corroded inside.
Battery must be load tested or specific gravities checked (no one does this anymore).
But it does just sound like alternator.
There is tons of info out there to troubleshoot, this is not a vehicle specific system.
Try this for forum search, all forum search engines are poor-
VW TDI Search Engine

Click to expand...

I suspected my battery wires were getting bad. I added additional heavy gauge wire from the terminal to the posts they connect to on the starter or block or body ground respectively. It's ghetto, but I have 0.3 ohms to everywhere I check. Block, body, alt case (from neg battery term) or starter or alternator post (from pos batt term).

I'm fairly certain this isn't an alternator issue as I outlined in my post above. My battery light doesn't come on. I don't have any chafing of wiring under the battery tray or inside the channel where the wiring harness runs under the airbox.

When the engine runs it should make roughly 14 volts. If not, something in the charge system is amiss.
Haven't watched this, but it might be helpful-

mattg said:

No the charging light / battery light does not come on with the key.


I know I need to fix this before I can start going down the road of a second bad alternator.

Click to expand...

The alternator get the voltage to excite the field initially from the charge light circuit. If the charge light does not light it wont activate the alternator. Fuse 11, 5Amp is the one that feeds the cluster and charge light. If that is good, ground the blue wire at the alternator connector and see if it lights then to test that circuit. The alternator grounds that circuit to light the light, and once activated the alternator is no longer a ground so the light goes out. You could monetarily touch voltage to the blue wire and the alternator will wake up and work if it is able to.

pdq import repair said:

The alternator get the voltage to excite the field initially from the charge light circuit. If the charge light does not light it wont activate the alternator. Fuse 11, 5Amp is the one that feeds the cluster and charge light. If that is good, ground the blue wire at the alternator connector and see if it lights then to test that circuit. The alternator grounds that circuit to light the light, and once activated the alternator is no longer a ground so the light goes out. You could monetarily touch voltage to the blue wire and the alternator will wake up and work if it is able to.

Click to expand...

I guess how the light ever lights up confuses me a bit and i'm trying to find a good diagram on it.

Fuse 11 is good.

Also, i'm not sure what you're saying.

I've grounded the blue wire, no voltage change.
I put +12 to the blue wire, no voltage change.

Those things make me think it is ALSO a bad "fresh" alternator.

But I'll try both wires again.

mattg said:

But I'll try both wires again.

Click to expand...

I put +12V to the blue wire on the alternator for 2 seconds and the alternator started making power. I applied the power at the connector above the starter so I know that from there to the alternator is good.

How do I troubleshoot this further?

mattg said:

I guess how the light ever lights up confuses me a bit and i'm trying to find a good diagram on it.
Fuse 11 is good.
Also, i'm not sure what you're saying.
I've grounded the blue wire, no voltage change.
I put +12 to the blue wire, no voltage change.
Those things make me think it is ALSO a bad "fresh" alternator.
But I'll try both wires again.

Click to expand...

You should have 12 volts to the blue wire at the alternator with the key on.
Fuse 11 feeds to the dash cluster 'control module' which goes to the dash light (LED).
From the LED it goes to the alternator via the blue wire.
Check power in the slot of fuse 11, 1 side should have power.