2) In steady-state flight, both of us hear a "woo--woo--woo..." softly in
the headphones. It sounds just like strobes that aren't grounded properly.

3) The noise slows down -- or speeds up -- in synch with the prop RPM. At
2300 RPM, it's going a bit faster than once per second -- maybe around three
times every two seconds.

4) I switch our digital voltage/amperage meter to AMPs, and watch as it
oscillates in time with the noise. It's alternating from 5 amps to 10-11
amps, in time with the "woo--woo--woo"... Voltage appears to be pretty
steady at around 13.8-ish volts.


Jay,

Is this not the "Cherokee oscillating Ammeter" thing? Mine has it. Exact
same symptoms. Had it for 11 years and 4 different alternators. Either
the split master switch (alternator side) or the alternator breaker
having a high resistance connection (either the wires or the
switch/breaker itself).

Google it. You should see lots of hits. A common problem if I recall.

Mike