Jay Honeck wrote:
When we flew our '75 Warrior, it developed a problem with the
alternator going off-line in flight. This was preceeded by the
ammeter needle bouncing crazily and finally pegging at 60 amps. [...]
The main culprit was a wire connector that was screwed into the
backside of the alternator with a simple phillips screw -- no safety
wire, no loc-tite, no nuthin'. Looked like a ground wire to me, but
I'm no mechanic.

Disclaimer: This is based on experience with ground vehicles and by
looking at the generator setup on a 182. I don't have an A&P; I don't
even have a TG&Y. Some of this may not be allowable owner maintenance.
Some of this may not be allowable on a certificated aircraft. Your
mileage may vary.

Sounds like the field wire to me. A loose ground wire would probably
tend to make the ammeter read less (discharge), rather then pegging at
max charge.

There are some variations, but in general, a generator or alternator
with external regulator will have three connections:

- Main output wire. This carries all of the current coming out of the
generator or alternator. Usually the fattest (thickest) wire on the
device, and often bolted on to a fairly substantial stud - 0.25"/6.3
mm or more diameter. The stud will be insulated from the metal case
of the machine.

- Field wire. The regulator turns this on and off to control how much
current the main wire puts out. This is a relatively thin wire (on
the order of 14 gauge or 1.5 mm^2) and may be bolted to a stud or
screwed to a metal terminal. The stud or screw will be relatively
small, like #8 or #10 (maybe 3 or 4 mm). The stud or terminal will
be insulated from the metal case of the machine.

- Ground connection. Often done through the mounting bolts, but some
may have a separate ground wire or strap. It will be at least as
thick as the field wire and possibly as thick as the main output wire.
It may also be a woven metal strap instead of a wire. This will be
bolted directly to the metal casing of the machine with no insulation.

Again, there are variations, but this is probably the most common setup
on older aircraft.

Of course, the first place I looked was the backside of the
alternator, and, lo and behold, the same damned wire was loose! A
few turns to tighten, and voila! -- no more whine [in radio audio].

Before you fiddle with this, make sure the master is off. For extra
safety, disconnect the battery negative cable.

Look at the place the screw goes into. Is there a plastic ring or boss
around it, insulating the screw from the case of the machine? If so,
then it's NOT a ground wire, and you CANNOT safety wire it to anything
that is grounded.

Also, look to see how contact is made. There should be a ring terminal
on the end of the wire. If there is a fairly substantial ring of metal
on the machine under the ring terminal, such that it contacts all of the
ring terminal all around, then that's probably where most of the
electrical contact happens, and the screw threads are just there to hold
it down. (If not, see "A" below.) In this case, I would consider this:
Get an aircraft-approved screw with the same thread as the existing screw,
plus a hex (internal or external) head. Also get an aircraft-approved
flat washer that fits the screw. You'll also need some brake cleaner or
alcohol, the lowest grade of Loctite, something like a Q-tip, compressed
air, and maybe some masking tape. Loctite comes in different grades and
usually has a note like "can be disassembled with hand tools" or "must
use power tools and/or heat to disassemble" on the package. You want
the "hand tools" kind, which _will_ come apart when you want it to.

Make su master off, battery disconnected. Unscrew the existing
screw. Apply brake cleaner or alcohol to Q-tip and clean ring terminal
on both sides; let it dry. Apply brake cleaner or alcohol to a fresh
Q-tip and clean the screw threads; let it dry. If there is any
possibility at all that you will get liquid into the generator/alternator,
cover the holes with masking tape. Then put brake cleaner or alcohol on
a fresh Q-tip and clean the place where the ring terminal bolts down -
get down in the threads if at all possible. Let it dry for a few minutes,
then give a gentle quick shot of compressed air in the threads to make
sure it's dry. Assemble the washer onto the new screw (rounded edge away
from screw head), then put the screw+washer through the ring terminal.
Hold the screw+washer+terminal near the place it screws into, and apply
the tiniest drop of Loctite that you can to the screw threads. (It may
be helpful to put a drop of Loctite on a cleaned piece of solid wire,
safety pin, etc, and then use that to put the Loctite on the threads,
instead of trying to squeeze the Loctite directly onto the threads.)
Start installing the screw, being very careful not to get any Loctite
anywhere other than on the threads. If you get Loctite on the ring
terminal or on the place where the ring terminal seats, take it apart,
clean everything, and start over. Once the screw is finger tight, get
the proper wrench or Allen key and torque it to spec. Remove any masking
tape that was applied and reconnect the battery. Count your tools. Do
a test run.

A: On the other hand, if the underside of the ring terminal is not totally
in contact with metal, then some of the electrical contact may be taking
place on the threads and Loctite may not be advisable. The best answer
in this case is probably to install an approved lockwasher under the
screw head (it should go screw, lockwasher, ring terminal, machine),
torque to spec, and inspect regularly.

Disclaimer: This is based on experience with ground vehicles and by
looking at the generator setup on a 182. I don't have an A&P; I don't
even have a TG&Y. Some of this may not be allowable owner maintenance.
Some of this may not be allowable on a certificated aircraft. Your
mileage may vary.

Matt Roberds