>Comments/Questions: I have alternator noise in my Sigtronics 
>intercom.  I re-wired and re-routed the harness out of the tunnel 
>(Glasair III) to around the cockpit - no help.
>
>I get alternator noise with the intercom on, quiet with it off, and 
>/or the ALT CB pulled.  I also get aditional noise when the fuel 
>pump or flap motor are run (but not always).  I'm kinda stumped.
>
>I've [now] been told that pulling the CB can hurt the alternator...true?

    No

>Also that a bad diode in the alternator can cause this noise?

    Sometimes . . . but if you have other accessories
    that cause noise too . . . then the problem is
    most likely more general and involves how the
    intercom was installed.


>I had the alternator rebuilt to no effect, so I thought that had 
>eliminated the alternator, but I could be wrong.  I also have 
>replaced the (B&C) voltage regulator.
>
>Suggestions and/or help would be appreciated.

    I'm sorry to hear that you've tried so many
    hopeful and expensive fixes without positive
    result. I note that you are not currently
    subscribed to the AeroElectric-List.

    Early on (after reading your symptoms)
    I and others on the list would have steered
    you toward an evaluation of your ground
    system. The problems you've described are
    almost certainly a function of shared
    pathways in the ground system for both
    victim (intercom) and antagonists (alternator,
    flaps, etc).

    These issues are also addressed in the
    chapters on Grounding and Noise found
    in the AeroElectric Connection.

    If you do not have a copy of the Connection
    you can download it here:

http://www.aeroelectric.com/Book/AEC12A_PDF.zip

    I'll suggest also that you join us on the
    List for expanded support of your quest for
    solving this problem. Never met a noise dragon
    that couldn't be slain.


   Bob . . .