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Alternator (Ammeter) Problem (Piper)

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Old May 24th 15, 05:32 PM posted to rec.aviation.owning
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Default Alternator (Ammeter) Problem (Piper)

On Saturday, August 26, 2000 at 8:06:40 PM UTC-5, Rick Potts wrote:
I replaced the alternator in my Warrior (PA 28-151) this week and the
prior problem (the alternator dropping offline periodically, up until
the time it dropped offline and refused to come back on 200 miles from
home) has been replaced by a new problem.

The good news is the new alternator came online when I started the
Warrior's engine this morning and, according to the ammeter, started
producing electricity.

The bad news is the ammeter needle then started to wiggle back and
forth across the dial like a windshield wiper, from "0" on the left to
about "30" on the right, about two times per second. Varying the
engine speed didn't make a difference in how it behaved.

I measured the battery voltage (at the cigarette outlet) and it
remained steady at 14 to 15 volts. It didn't fluctuate at all, even
though the ammeter needle was dancing all around.

The Piper Service Manual's troubleshooting chart says that "excessive
ammeter fluctuation" can be caused by a defective voltage regulator or
excessive resistance in the field circuit. I hesitate to blame the
voltage regulator when the voltage stays so steady, so is "excessive
resistance" the likely culprit?

For "excessive resistance" the manual recommends: "Check all
connections and wire terminals in field circuit for deterioration such
as loose binding posts, broken wire strands at terminals, etc..
Tighten all connections and replace faulty terminals."

I'm no expert at reading electrical diagrams, but it appears the
"field circuit" would include the voltage regulator, the overvoltage
relay and the alternator switch. The output side would include the
ammeter and a large (6 gauge?) wire that runs to the battery

The voltage regulator and the overvoltage relay are mounted up under
the instrument panel, so getting to them won't be easy. The alternator
switch, on the other hand, is quite easy to get to so I think I'll
start there.

Question: How is the split master switch mounted? Does the plastic
cover piece come off the instrument panel with the switch mounting
from the front? Or do I have to remove it from the rear somehow? I'd
like to get in there to clean and tighten whatever connections are

Or is the voltage regulator still a potential culprit?

Thanks for any ideas!

Rick Potts Phoenix, Arizona
N32334 PA 28-151 Warrior

Had a puzzling week with a 1978 Warrior doing the same thing with Load meter, finally located a chafed Alternator output wire to Primer line which now all adds up.

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