"Tom Jackson" wrote in message news:cS8ic.10690$_L6.913327@attbi_s53...
The other day, I was flying and noticed that my ammeter guage was reading 0
(it had been reading fine for a long portion of the flight.) Also, I had
been running a lap-top from the cigar lighter plug for the first time ever.
I turned-off virtually all electric devices and continued to my destination.
I also shut-off the alternator switch. Later in the flight, I tried
recycling the alternator switch, and the guage would read full deflection,
so I then would shut the alternator switch off again.

Later in the day, I fired-up the plane - could tell that the battery was
weak because it could hardly pull the prop through. The ammeter guage,
however seemed to look ok - appeared to be charging the battery. I figured
that somehow it had recycled itself, so I took off and headed home without
incident (I watched the ammeter guage very closely throughout the flight,
and it appeared normal throughout.)

The plane is a 1974 Piper Warrior - 151.

Any thoughts? Was it merely a failsafe due to too much current being drawn
from the lap-top? Should I have it looked at?

I can't imagine the current to run a laptop being a factor. I have had
instances where the battery was so low that the alernator would charge
full scale and trip the alternator breaker with the engine at high
rpm. At idle it would charge less and the breaker would hold.
--
Gene Seibel
Hangar 131 - http://pad39a.com/gene/plane.html
Because I fly, I envy no one.