You did not say what was wrong with the amp meter.
If you replace the cluster Cessna will make sure that owner's pocket
will be picked clean because you will have to replace the fuel $ender$
also.
I have fixed several amp meters that had high resistance by just
tightening up the terminal nuts on the back of the case. The fiber
shoulder washers compress after a few years and remove the clamping
pressure on the shunt inside the case of the ammeter. This increases
the resistance from the terminals to the shunt and makes it run hot
and have too much voltage drop. This can cause all sorts of
interesting intermittent problems.
I would also look at the 60 amp alternator breaker. With age they
tend to trip at much lower currents and have too much voltage drop.

You can verify this with a 4 wire Kelvin ohm meter setup.
With a one amp load every millivolt is one milliohm of resistance.
John

On Wed, 11 May 2005 18:29:29 -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