I'm not an A&P, but have some electronics/electricals background.
Normally when you see that much oscillation in a ammeter, its either
the diodes in the alternator or the voltage regulator.

A local school was having the same problem with a recently acquired
Cherokee -- the neddle swung back and forth a good 10-15 amps varying
as the load changed. Got to checking and found an unmarked voltage
regulator in it. Checked with the owner who says "Oh yea, its from a
Saab! Works good, doesn't it?"

So, don't discount a wrong part in it. Just because its "worked"
doesn't mean its the right part.


Chuck



On Wed, 11 May 2005 18:30:35 -0700, "Paul Anton"
wrote:

I am hoping to tap some of the expertise here to solve a problem I have run
into.

I am a retired guy who was called by a local Part 141 school to fill in as
their flightline mechanic until they could find a permanent A&P. They have
an early 182RG (serial 141) that has an ongoing electrical problem.

My first question concerns the ammeter. I have definitely confirmed that the
ammeter is defective. It appears like the ENTIRE gage cluster will have to
be replaced. The parts manual shows that the original gage is not available.
A supersession was listed which also consisted of a single gage. However
when this was pursued it was not available as a single replacement.

So my question is has anyone come up with a solution for a single defective
gage in this cluster that does not involve replacing the entire thing? How
about an instrument shop that would rebuild the ammeter? I have been unable
to find an instrument shop that would bother with an ammeter.


Here's my second question. I think the reason the ammeter broke is that it
simply wore out. The voltage and hence the current is constantly varying.
The original ammeter needle was oscillating so much that you couldn't tell
if the system was charging or not. I put a test ammeter in series and the
although the ammeter could be read, it was still oscillating. A check with
an analog meter showed fluctuations that increased in frequency as the RPM
was increased. Ditto for increasing the load. A scope shows about 900 mv
peak.

Persons before me have replaced the alternator and regulator. (a note here,
the regulator is the simple 3 wire unit)
All grounds were cleaned and remade.

Any hints of where I should begin my search would be greatly appreciated. I
have to pull this beast out of the hanger to run it up. With out Northwest
weather I haven't had two clear days to work on it outside and I'm too old
and stiff to do a lot under the panel. So any hints or experience of a
similar trouble would really be appreciated.

I'm going to jumper the alternator field portion of the dual master switch
to start with but beyond that ----------------


Thanks in advance

Paul Anton