I recently had to replace my alternator as the one original to the car died after 180k miles. The new unit is a Subaru re-manufactured alternator purchased from the dealership.
The original failure of the alternator was confirmed by taking my car to a local place that could do charging system testing. It showed there was zero voltage being delivered by the alternator. After replacement, I had it retested and the voltage is great with minimal flutter.
The problem now is that the battery light remains lit on the dashboard.
Here's what I currently know and have tried:
- As mentioned above, a charging system test came back positive.
- Using an OBD2 scanner I show a good charge level.
- The battery is tested and is good.
- The brake and battery light are both lit, but I gather this is normal for this generation of Legacy.
- I can pull the 3-pin plug from the back of the alternator and the lights go out.
- There's no voltage coming from the sense pins on the alternator.
- Voltage across the 10A alternator fuse in the engine bay was 11.7V. Voltage at the top post of the alternator was 12.4V.
The one variable, and possible red herring, is that I've also just replaced all the incandescent wedge bulbs in the instrument cluster with equivalent LED units.
Another new twist is that there's an audible whine now coming from the new alternator. This developed after a short trip to a store about 5 minutes from my house. The belt is not over-tightened as there is a small amount of play in it.
Any ideas about how best to diagnose or check this would be very appreciated.