Mike Noel wrote:

For what it is worth, my alternator started going off-line regularly after
months of perfect operation. With some investigation I realized the trouble
started when I 'rediscovered' the electric trim on my 74 Archer. Even
though the trim would move OK with no noticeable deflection of the ammeter,
after a while I would look down and see no output from the alternator.
Cycling the alternator field rocker would put it back on-line. Not sure
what the problem is with the trim circuit since the trim wheel doesn't seem
to have too much friction, but now I trim manually and will eventually
investigate the wiring and motor.

The inductive voltage spike from the trim motor (at the instant you
release the trim motor switch) is being detected by the alternator
OverVoltage Protection (OVP) circuit built in to the Piper's Alternator
Control Unit (ACU).

The solution: supress the motor glitch (at the motor), or make the
OVP less susceptible to a momentary voltage excursion above 16V.

The topic has been extensively discussed on r.a.o before. Google groups
it...

MikeM
Skylane '1MM
Pacer '00Z