alternator wiring

Hi everyone,

I'm troubleshooting some battery no-charge problems on an 01 Jetta. I've cleaned the ground beneath the battery tray and tested the continuity and resistance on the wires going to the alternator and starter. The two pin connector to the alternator actually only has one wire populated. It's the L pin according to the Bentley and this wires up to the loom via pin 2 (blue wire) at the 4 pin connector near the starter. When I turn the ignition to ON, I'm getting battery voltage on this pin but the battery light is _not_ lighting up on the dash. Isn't it supposed to? An instrument output test in VCDS doesn't light up the LED either.

With the car running, I've measured the voltage between the alternator output post and ground and I'm getting battery voltage instead of 13.5V+.

If I'm getting voltage at the L pin to the alternator, do I care about the battery light at the dash at all? The postings I've read here and via Google suggest the light is wired directly to L and is responsible for exciting the alternator.

If I run a jumper wire from the two pin alternator connector to ground, can I expect the battery LED to turn on?

Or is it time for a new alternator?

I ran a jumper from the L pin of the connector to the ground post on the battery and the battery LED lit up on the dash.

I'll take the alternator to a shop tomorrow to see if it can be saved.