Posted for "glong2" <glong2@netzero.net>:

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 I have had a very similar problem that I have not solved. I have two B&C
 regulators, one tied to the Continental 70 amp alternator and the other to a
 20 amp B&C alternator..
 
 The only time I have parked the plane outside overnight was on a short trip
 over Christmas. It got down to about 20F with a lot of frost. I cleaned off
 the wings& tail and hooked up an engine heater to warm the engine up before
 starting. After I started ( it started easy), my main alternator was not
 putting out any current. My B&C alternator/regulator were working fine. I
 taxied to the runway with no main alternator using the B&C alternator to
 charge both batteries. I did the preflight run-up check, and when I came
 back to idle the alternator started working. It has not quit since!
 
 It is hard to trouble-shoot when all is working as it should.  Since my
 regulators are inside the cabin, I am speculating it is a regulator problem
 that is sensitive to cold temperatures. The cabin did warm up during the
 taxi and engine run-up. The airplane has not been parked outside since then
 so I have the problem on my questions list!
 
 Eugene Long
 Lancair Super ES
 glong2@netzero.net
 

"""
  I have a B&C 14 volt, 60 amp alternator as well as one of their voltage
 regulators.  They were trouble free for about two years until about 5 weeks
 ago when I went to go fly and couldn't get my alternator to come on line.
 It was an uncharacteristically cold and damp day when this happened (my
 plane is hangared, so it wasn't wet).  After an hour of fruitless
 troubleshooting, I had to cancel my flight and head for the airlines to get
 where I was going.
"""