You sure you are not flying a Cessna Skymaster?  

1.  Who made your alternator, voltage regulator, and battery?  This is not
likely to happen with a "suite" of products such as B&C.  Is your regulator
"battery temperature" modulated?

2.  Is the ground (battery, engine, voltage requlator and bus) good?   I mean
really good.

3.  Have you used high quality switches?  Resistance in the alternator field
switch or regulator connection can lead to the dancing light syndrome.  If
the master switch has built up resistance,  it is possible that the voltage
for holding in the master relay is sometimes inadequate thus leading to relay
contact bounce which leads to arcing and carbon build-up which can lead to
unreliable main bus connections which can cause fluctuations on the bus
leading to fluctuations on the regulator which can lead to visible
fluctuations in lights but smoothed voltage instrument indications.

4.  What happens when you turn on pitot heat?  The alternator should be able
to handle that load - maybe you should turn on the landing lights at the same
time.

Verrrrrry Interrrrresting.

Scott Krueger
N92EX