At least there's no smoke or fire this time.  However, not sure exactly what's going on.  So far the new alternator is the prime suspect, with the battery (also fairly new, was replaced due to old age/not holding a charge well anymore) being a consideration as well.

For a little background, the alternator was recently replaced due to problems last Summer.  While idling the car in between runs at the local SCCA Solo event, I noticed that the voltage was dropping pretty low (12.3 - 12.5v vs. the normal mid to upper 13's).  The problem was definitely heat related as simply opening the hood would cause the voltage to come up a couple of points pretty quick.  No problems while driving though.

So, this year I decided to start with a new alternator.  It's a Bosch unit, rated at a higher output than stock.  I forget all the details, but it was the standard equipment for a different configuration of the same car (perhaps the Spyder?).  The first month no issues were noticed.  However, now that it's hot out I've run into another charging issue.  Everything works perfectly fine if the car is cold started.  However, if the engine is still hot (as in the car was shut off within the last 15 minutes), I have very low voltage.  Shows as 12.2v on the AFM display and 11.8 on the AFC (which always reads about .4v lower).  While in this state, the low voltage light doesn't come on bright like the alternator has failed, but all the dash warning lights have this faint glow to them (not even noticeable if there's any sun hitting them at all).  Reminds me a little of the big electrical fire I had, but they all came on real bright all at once when that happened!  Anyways, the voltage does jump up again all of a sudden eventually (within a couple minutes, but the longer the car sat, the shorter this interval is) and everything's fine again.  No problems while idling hot, just on the startup.  The voltage also seems to pop back up faster if the car is driving rather than idling waiting for it to come up after the start.  If idling and the voltage jumps up, the rpms drop 200-300 immediately, so it appears like the alternator is just deciding not to do any work (and not load the engine any), rather than having some sort of weird short circuit diverting power.

At this point (after discussing it with my mechanic), we've decided to just wait and see.  There's a 1 year warranty on the alternator and I'll just try to avoid long trips out of town.  Staying within 100 miles of home with the car should leave me enough power to make it all the way home on battery even under the worst conditions...  The downside here is that it pretty shoots any plans of running any Road Rallyes this season and makes me question even doing any Solo events (since the car idles for long periods of time without me monitoring the voltage).  Oh well, maybe I'll just go flying instead!  :)