Greetings oh wise and powerful List.
The last week or so I have noticed my 71 amp gauge needle swinging back and
forth off center when my engine is above about 1800rpm. During idle and up to
about 1800rpm the needle is in the middle or slightly on (+) side as normal.
With increased rpm the swinging back and forth of the needle increases in
frequency.
At first start of the engine the red IGN light is ON as normal and the amp
gauge needle is slightly on the (-) side as normal. Then I raise rpm above
about 1500 and the alternator then puts out a charge and the red IGN light
goes
OFF. While idling the amp needle is steady in center (or slightly on (+)
side) and DVM at the battery posts reads a steady 14.7VDC to 14.8VDC as normal.
Then I bumped up the idle screws to bring engine speed to 2000rpm and now
the DVM at the battery reads a fluctuating value from 12.8VDC to 14.8VDC. The
fluctuation of the alternator output is so fast that DVM is only picking the
variation up as it swings up and down and I cannot get a steady reading as when
engine is idling.
PO installed an AC Delco 63A alternator (stamped 1103121, 63A, 9K22,
12VNEG). Several months ago tracing a dying battery, I found the voltage
sensing
wire was not wired properly as it was connected to the alternator output. Thus
it was sensing 14.8V so only a trickle charge was being sent to maintain the
battery charge. I since fixed that wire connection (thanks Dan Masters!) and
removed, cleaned, reinstalled the amp gauge to ensure good connections and all
has been well until a week or so ago. I did have the alternator checked out
months ago when I was tracing the battery fault and per AutoZone checked out
fine.
I wonder if internally I have diode or something that is failing causing the
voltage output drop with increased engine rpm. But what I do not understand
is why at idle speed the voltage output is steady and amp needle reads normal.
I doubt this has anything to do with the voltage regulator on the rear of
the speedo right? I am leaning to alternator internals failing.
Night driving is out as the headlights are pulsing the entire time while
driving and I do not need that kind of attention! However sitting idling at a
stop light they are steady with no pulsing.
Many thanks,
MRankin, 1971 TR6 CC61212L
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