20v mysterious dash light warnings?

[Thompson Smith <thompers@together.net>]

Greeting, This message posted for a friend...
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For no apparent reason the battery, brake and parking brake lights on my
dash appear.  The voltage meter does not seam to be affected (it reads
normal), and the performance and general condition of the car and other
computer systems do not seem to be affected.  Except for my climate
control system which will constantly turn on and off when these dash
lights are acting up.  I can stop the climate control problem by putting
the heater on defrost low (any other mode will still be effected). 
Another peculiar piece to this puzzle is that when the engine is revved
up past 3000 rpm’s the warning lights fade off and do not appear again
until the rpm’s drop below 3000.  Also, this problem does not have a
consistent pattern. One morning I just pulled over and restarted the
engine and that solved the problem.  And yesterday they stayed on for a
day and a half and then when away.  I haven’t found a correlation to
link this problem to yet.  What could this be?
Matt Noonan
1990 Coupe quattro 20v
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Thompson Smith