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home) has been replaced by a new problem.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
contactor.

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
there.

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.

On 2015-05-24 16:32:19 +0000, said:

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
contactor.

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
there.

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.

I bet you its gonna turn out to be the voltage regulator. Had similar
experience. Mostly needs just a little adjusment. Good luck.

I'm working on a Piper Cherokee that's ammeter is showing a mild draw and then a drop. It maintains a measurement of 10amps for maybe 10seconds then it drops back off to zero. The pilot removed the alternator took it to get tested then brought it back. The pilot also had the voltage regulator changed out. Anyone had a similar problem? I can answer more questions this was just a brief description.

On 2018-10-29, wrote:

I'm working on a Piper Cherokee that's ammeter is showing a mild draw
and then a drop. It maintains a measurement of 10amps for maybe 10seconds
then it drops back off to zero. The pilot removed the alternator took it
to get tested then brought it back. The pilot also had the voltage regulator
changed out. Anyone had a similar problem? I can answer more questions this
was just a brief description.

Speaking as a Cessna driver, I see this routinely (although my meter kicks
up to 20 or 30 amps when I first fire up). The alternator is replenishing
the charge that was drawn from the battery by the starter; the meter settles
back down to zero after a minute or so when the battery is topped up.

However, in a Cessna the ammeter measures how much juice is going into
or out of the battery (it goes positive or negative), whereas in a
Cherokee the meter indicates how much the alternator is putting out,
regardless of what's happening to the battery. It can never give a
negative indication. Upon starting, the meter would show the charge
the alternator is putting back into the battery, in addition to whatever
other electrical loads are on the bus. After the battery is topped up,
the meter should drop to what was required to supply whatever electrical
devices are turned on. If you haven't yet turned on lights, radios,
etc. this would be close to zero. (Sorry, I forgot to closely watch
the ammeter on startup last time I flew a Cherokee.)

Have you tried putting a load on the system? Once the engine is running
and the meter has dropped to zero, try turning on the landing light.
You should see a good indication on the meter then. If not, there's
a problem somewhere. Make sure the landing light isn't burned out,
though. :-) (I recently detected a burned-out landing light in broad
daylight by this lack of response on the meter.)

--
/~\ lid (Charlie Gibbs)
\ / I'm really at ac.dekanfrus if you read it the right way.
X Top-posted messages will probably be ignored. See RFC1855.
/ \ Fight low-contrast text in web pages! http://contrastrebellion.com