On Mar 12, 6:17 pm, "Travis Marlatte"
wrote:
"RST Engineering" wrote in message

...

A coup'la questions & comments:

1. Why would you disconnect the battery to replace the alternator?

I suspect it was in an attempt to reseat all connections that could
contribute to the problem. I had already done this as well as "moving" all
of the alternator mounting bolts. I didn't try any magic juice, however.



2. One presumes certain basic troubleshooting procedures prior to
throwing parts at the problem, like back all heavy nuts grounding the
alternator, squirt in a little magic juice, and retighten.

I'll emphasize that I did my own diagnosis and concluded that it was an open
diode. I took it to the shop not to have them diagnose but to swap the
alternator - which they did quite well and it (or the process of doing it)
solved the problem.

-------------------------------
Travis
Lake N3094P
PWK

We once had an alternator whine in a 172. The alternator
wasn't the problem; there was a ground loop somewhere. After messing
endlessly with ground straps and filters and other connections, I
finally got fed up and ran the alternator using our table saw motor--
wheeled the saw up to the front of the airplane and used the belt to
spin the alternator while I got under the panel wearing the headset
and used a jumper to try grounding/ungrounding various jack points.
Managed to minimize the whine by moving a groundpoint to a point where
a bunch of other avionics grounded. Old airframes develop resistances
at riveted joints, causing a voltage drop across certain components
and introducing noise that's supposed to be filtered out in the radios
or audio panel. I think. Anyway, it worked.

Dan