Lacking any responses here, I did some more research on the 'net and found
several references to climate control problems with these cars.  

Again, the problem that I'm seeing is an intermittent failure where the
fan simply does not come on when commanded.  So far, this has only
happened when the car has 'heat-soaked' for awhile in the sun.  Somewhat
annoyingly (and humorously), my A/C works perfectly except when I need it.

Although it didn't look like exactly the symptoms, I thought it couldn't
hurt to reflow the solder at several key spots on the control computer and
replace the capacitor (instructions found via google search).  

I did that procedure, but the problem remains, so I've determined that it
_MUST_ be the 'final stage unit' (device that provides staged power to the
fan itself as commanded by the climate control computer).  I located it
under the dash on the driver's side, right by the firewall and secured by
2 Torx screws into the heater duct.  It has a black 5-pin connector.  

My local dealer quoted me $146 for the part, so I ordered it from
www.bavauto.com for $109+S&H (not the cheapest on the 'net, but a good
price and a reputable outfit that I've dealt with before).  It hasn't
arrived yet, but I expect it next week.

At this point, I'm pretty sure that's the problem (enough to risk $100+).
I'll post again if it should turn out that I'm wrong...

Dave