New alternator & battery not charging

Vehicle is a 2003 TDI Beetle w/manual trans and all the options

The short version
Intermittent charging light, battery mysteriously died, replaced battery, discovered charging light only comes on at higher RPMs (voltage regulator overcharged battery?), family member replaced alternator with rebuilt unit from O'Reilly, battery discharged after one day stranding wife, talked O'Reilly into a new battery.

Disclaimer: I had a busy week at work so I trusted others to do everything prudently and correctly.

Now that I'm becoming more intimate with this problem - i.e. Reading manual and TDI Forums and enlisting the help of a trained mechanic friend - I'm trying to rule out other possibilities before going to all the trouble of replacing the alternator again. Here's what I know:
1. Battery light no longer goes on when key is on.
2. When car is running the volt meter is under 12 volts and doesn't rise when rpms go up.
3. Cable coming from fuse block to POS terminal is bent funny and could be suspect.
4. My Autel code reader doesn't come up with any faults.

I'm open to any suggestions.

First off, go get a volt meter $10-$20 on amazon or harbor freight.
If the battery reads less less than 13V or over 14.5V when running, the alternator is dead. Buy a new OEM BOSS.
thats it. Good luck

Don't forget, you must have the correct alternator pulley (clutch type) for the TDI. I doubt very much that an O'Reilly Chinese alternator will come with the correct pulley. The old alternator will have the correct one on it, unless you turned it in already.

do not buy these parts as a reman, or as anything other than OEM. EVER
CV axles
brake caliper parts (rebuild them with new seals vs replacement) 3 times now i have had to take apart a Reman because it has sand in the caliper piston area and was binding. left from the reman process)
Alternators
Water pumps

Sage advice. Some guy posted that he installed a garbage Chinese turbo from some parts house and it immediately crapped it'self.

What impressed him the most was that the parts house included FREE gaskets with the 2nd Chinese turbo they gave him.

Lets see: "I realize that their Chinese turbo destroyed my engine, but hey, I got free gaskets".........

Troubleshoot first. For all anyone knows the problem could be with your wiring (alternator to battery- a not all that uncommon problem).

Make sure, however, that any replacement alternator is actually for a TDI! It MUST have a clutched pulley.

make sure there is battery voltage going to the regulator, the alternator needs to have the field windings excited to get voltage reading off the battery

alame said:

make sure there is battery voltage going to the regulator, the alternator needs to have the field windings excited to get voltage reading off the battery

Click to expand...

WHAT? who told you this?
Maybe some new extravagant cars alternator or something but not any VW 2003 or not that I know of! All you have to do is spin it and it will output voltage. Its DC current, it flows ONE WAY, no metering of the battery is necessary. What happens is that the voltage regulator has a resistor and some other components in it that makes any output at a steady 13.6 or 14 volts depending on the part or car. I know this very well as I have used them as power generators before with no battery what so ever. They still output exactly the same voltage as it will connect or not. What can change the volts is the amps draw on the battery and thus pulling more amps creating more impedance. This is why when you turn on your radio and lights the votes goes from say 14 to 13.8. One volt is equal to current of 1 amp time’s resistance of 1 ohm: 1V = 1A ⋅ 1Ω.
Op just got a reman POS that does not work, that’s all.

You did check the main fuse on top of the battery as well as its connection?

I did suggest checking charging voltage at the alternator. Even with a blown fuse you would still get voltage there.