(Jay Masino) writes:

I disagree; many alternators I've seen have an added ground wire.
The engine sits on rubber motor mounts, you see...

Most aircraft have a heavy "battery cable" (for lack of a better
description) connecting the engine case to the airframe. Because of
this, the rubber lord mounts are generally irrelevent.

So do cars, but.... The only grounds you KNOW will never vibrate loose,
get corroded, you name it.. are the ones that don't exist.

The alternator is bolted down to the block, surely that's good enough,
right? May I introduce you to a gentleman named Murphy?

A classic Car-Talk "stump the chumps" type question involved now-25+yo
MOPARs. [Think fully size Plymouth Fury, etc.]

Why do the headlights get BRIGHTER when you step on the clutch or the
brakes? The engine-to-frame bond was failing. The drivetrain was mostly
isolated by rubber mounts BUT the clutch fork etc. was a substitute
path. Applying the brakes made drum contact and there was a parking brake
cable, you see... I've even heard that the current through same would eat
the driveshaft U-joint bearings.

The alternator noise he described is symptomatic of two possible causes:

a) Bad alternator diodes.

b) ground grief: either a missing one, or an added one in a audio circuit
[aka ground loop].

I always think "grounds" first thing when some talks of noise...



Jay surely knows the difference between a wire screwed to the case;
and one going to a terminal...

Not necessarily.

Well, I'll keep my faith in him for now.


[Do aircraft installations of his vintage even use screw terms for
field/aux alternator connections? Autos have used latched plugs for
decades with only the large high current output wire being a stud &
lug...]


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