On Mon, 16 Feb 2009 21:41:07 +0000, Mike Harvey
wrote:


Hello, I own a 65 m20e with a io360. Recently been experiencing noise
on com1 and have read about low voltage being a problem with nav/com's.
I have a king ki 165 for both com1 and com2. I've tried to diagnose the
problem and it appers that my alternator isn't charging the batter
correctly nor is it bringing the system bus up to 14volts. I've
noticed this via a volt meter to the 12 volt(car type) adatper(although
i don't know if this is the correct procedure) and I've also made notes
of the bus voltage before starting and after shutdown on a long flight
and it went from 13.5 volts to 12.2 volts(enging off). Does this seem
like it could be a low voltage noise from a alternator not charging
correctly. If so has anyone had experience repairing alternators on
m20e. I would imagine a new one would cost around 1K. But I don't
know.

Thanks

Mike

A fully charged 12V battery should read 12.7V with everything turned off
for a few hours. So either there is a significant voltage drop to your
cigar lighter, or your voltmeter is not accurate.

You could have loose or corroded connections anywhere in the circuit.

What kind of alternator? -- the original had a generator, but there have
been STC's for various alternator mods.

I've not had noise as a radio problem (in my 65 M20E) with 13+ volts on the
bus (KX155 radio). With low voltage (under 11-12 or so, can't recall
exactly), the first thing that seems to go is the squelch.
--ron