Broken alternator?

[JonathanT]

In my '99 450 with serpentine enginer, the battery light is continually on irrespective of how fast the engine is going. I've checked (and replaced) the 100A fuse which was all ok. The big terminal on the back of the alternator shows 12.5V and across the battery also shows 12.5V. When the engine is running the battery shows 12.0V (or thereabouts).

Does this mean my alternator is probably broken?

[JonathanT]

Thanks everyone, I'm taking the brain dead option and getting my garage to replace for me. I'll see if I can get the original magnetti refurbed by someone more competent than me so I'll have a spare for next time.

[JonathanT]

I'm taking a punt on the one from tvr-parts because it's not stupid money. I had a go at removing the old one this morning and gave up at "getting the bolt sleeves out" because access was so poor.

[JonathanT]

Does anyone have any recommendations for getting my old alternator rebuilt in the Cambridge-ish area?