Usually the hand on my ammeter bounces for a few moments while taxing
and then settles down at about 20 amps. Yesterday it continued to be
erratic with a few calm moments with the hand indicating 10 amps. The
ammeter has 1976 stamped on the back. Do these things ever wear out?
Is there any way to bench test one? I need a few opinions, what is
the most likly culprit - ammeter, regulator or alternator? Thanks Leo

In article >,
(Leo) wrote:

> Usually the hand on my ammeter bounces for a few moments while taxing
> and then settles down at about 20 amps. Yesterday it continued to be
> erratic with a few calm moments with the hand indicating 10 amps. The
> ammeter has 1976 stamped on the back. Do these things ever wear out?
> Is there any way to bench test one? I need a few opinions, what is
> the most likly culprit - ammeter, regulator or alternator? Thanks Leo

from the Cherokee hints & tips, there are several potential causes.
Most are related to loose connections or corroded connections (the
connection heats up, becomes open, cools off and closes). The time
I had a bouncing ammeter, it was caused by a bad master switch.

Checking and cleaning all the connections is the cheapest first step
in troubleshooting this (assuming you are doing it) rather than trying
to isolate the problem by swapping out the ammeter, regulator, or
alternator.

--
Bob Noel

We had the problem of bouncing loadmeter needle in our 74 Archer. It came
and went, but it bothered everyone because no one could guarantee that it
wasn't a sign of impending trouble, even though a lot of people told us that
many, many Cherokees have that problem. We found a lot of potential fixes
in various places on the internet. One of the recommendations was to change
the regulator for a solid state one. One of our partners said this was too
much and that we should clean all the contacts before we invest in a new
regulator. So he and another partner spent most of a Saturday cleaning all
the contacts, including some in the alternator. When they put it back
together, there was no charging at all. Then they discovered that the extra
washer they had when they were done was an insulating one, and that they had
shorted the field winding to ground. This had fried the (solid state)
regulator, so nothing worked even after putting the washer back where it
belonged. So finally, they turned it over to the A&P who reassembled the
alternator, replaced the regulator (with a solid state one, again), and
checked everything out. Everything now works perfectly. No needle bounce,
rock solid. Unfortunately, we will never know if the problem was the
regulator, a loose connection, or dirty contacts. We're also a few hundred
$$'s poorer.

--
Bob (Chief Pilot, White Knuckle Airways)

I don't have to like Bush and Cheney (Or Kerry, for that matter) to love
America

"Bob Noel" > wrote in message
...
> In article >,
> (Leo) wrote:
>
> > Usually the hand on my ammeter bounces for a few moments while taxing
> > and then settles down at about 20 amps. Yesterday it continued to be
> > erratic with a few calm moments with the hand indicating 10 amps. The
> > ammeter has 1976 stamped on the back. Do these things ever wear out?
> > Is there any way to bench test one? I need a few opinions, what is
> > the most likly culprit - ammeter, regulator or alternator? Thanks Leo
>
> from the Cherokee hints & tips, there are several potential causes.
> Most are related to loose connections or corroded connections (the
> connection heats up, becomes open, cools off and closes). The time
> I had a bouncing ammeter, it was caused by a bad master switch.
>
> Checking and cleaning all the connections is the cheapest first step
> in troubleshooting this (assuming you are doing it) rather than trying
> to isolate the problem by swapping out the ammeter, regulator, or
> alternator.
>
> --
> Bob Noel

The Ammeter on my 75 Warrior used to bounce all over the place and after I
replaced the voltage regulator it went away. As others have pointed out
loose connections are also a likely culprit. FWIW - the voltage regulator
was in the neighborhood of $100.


-Brian
N33431

"Leo" > wrote in message
m...
> Usually the hand on my ammeter bounces for a few moments while taxing
> and then settles down at about 20 amps. Yesterday it continued to be
> erratic with a few calm moments with the hand indicating 10 amps. The
> ammeter has 1976 stamped on the back. Do these things ever wear out?
> Is there any way to bench test one? I need a few opinions, what is
> the most likly culprit - ammeter, regulator or alternator? Thanks Leo

On 3 Dec 2004 14:08:35 -0800, (Leo) wrote:

>Usually the hand on my ammeter bounces for a few moments while taxing
>and then settles down at about 20 amps. Yesterday it continued to be
>erratic with a few calm moments with the hand indicating 10 amps. The
>ammeter has 1976 stamped on the back. Do these things ever wear out?
>Is there any way to bench test one? I need a few opinions, what is
>the most likly culprit - ammeter, regulator or alternator? Thanks Leo

99% chance the ammeter is ok, as are the VR and alternator.

Two most likely causes:
1. Bad master/field master switch. Contacts heat up, break contact,
cool, contract, and begin the cycle over again.

2. Intermittent resistance in the path from the main voltage bus to
the voltage regulator. The resistance can caused by corrosion of
failure of any one of the following components:
2a. Field current circuit breaker
2b. Connection from field current breaker to field (master) switch.
2c. Field (master) switch
2d. Connection fom field master switch to OVR
2e. Connection from OVR to VR

If your plane is a 1970s Warrior - these components are approaching 30
years old. Replacing the switch, circuit breaker and wiring is cheap
insurance against electrical failure.

-Nathan

My AMP meter in my old Arrow would bounce as well only when the strobes
were turned on (Whelan Comet Strobes) otherwise it was rock solid.
Maybe you have a current drain, or a loose connection someplace?

Leo wrote:
> Usually the hand on my ammeter bounces for a few moments while taxing
> and then settles down at about 20 amps. Yesterday it continued to be
> erratic with a few calm moments with the hand indicating 10 amps. The
> ammeter has 1976 stamped on the back. Do these things ever wear out?
> Is there any way to bench test one? I need a few opinions, what is
> the most likly culprit - ammeter, regulator or alternator? Thanks Leo