I think that you will find that the voltage spikes generated by the
trim motor and switch are getting into the voltage regulator's over
voltage sense and tripping it off line. You can suppress the
generation of the spikes with a 50 volt MOV (metal oxide varistor)
across the trim motor or add a capacitor across the regulators voltage
sense input or both. If the regulator already has a large external
cap replace it with a new cap since the electrolytic cap tends to dry
out and lose capacity over the years.
Do not add a cap across the motor or the switch may fail soon. To see
these spikes requires a digital storage scope which most A&P's do not
have.
John

On Fri, 23 Apr 2004 18:51:49 -0700, "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.