[Biturbos4] Brewing electrical problem?

[Mark R]

Sounds like voltage regulator ("VR," which is built into the alternator).

I think there's a small chance of an internally shorted battery, but from
the symptoms, VR is the 95% choice.

I've seen this before- only acting up when cold, on a 100K mile GM
alternator.  The only thing I can think of- the cold makes the load that
much more difficult and pushes the VR "over the edge."  In warmer weather,
everything was fine.  I originally mis-diagnosed it to an old battery.  New
battery DID help. but it got cold again and acted up.  Rebuilt alternator
(with internal VR) solved it for good.

Mark Rosenkrantz