Gentlemen -
Thank you for your replies. I'm digesting them, and will let you know if
anything develops.
Colin - no I can't be not sure if the stated RPM figure is for engine
RPM or alternator spindle RPM. I assumed it was engine RPM, for a couple
reasons. First, max cited speed is 6000 RPM. This is more-or-less red
line for the engine, so it makes sense to have a spec there. If it meant
alternator RPM, that would be only 2000 RPM (engine), which is only low
cruise speed. However, I do note that 6000 RPM (engine) means 18,000 RPM
for the alternator, which seems kinda high for a mass-produced commodity
metal item. Bottom line, I don't know.
I would love to fit a higher-capacity alternator, but space is at a
premium in that area. I'm not at all sure that I could wedge a
physically-larger unit in there. I was hoping someone had done so, and I
could leech on that knowledge.
Viggenist - all of my 900's have exhibited exactly the same stumble and
drop in RPM when a big load comes on at idle. In particular, when the
radiator fan comes on (you can hear it, of course), the engine very
nearly stalls until the control mechanism, whatever it is, brings the
throttle up. And when the battery gets close to dying, the engine does,
in fact, stall when this happens.
I'm sure that the brushes are in good shape, since they are part of the
voltage regulator assembly, which I replaced a few thousand miles ago.
I have confirmed that the problem is (almost) entirely load-related, and
not as RPM-related as I had thought. Yesterday I pulled into the
driveway and sat there with the engine idling. Voltage measured around
13.5, which is adequate but not generous. When the rad fan came on, and
after the stumble recovery, it was down around 12.8, which is not
adequate. By adding headlights, and then air conditioner, and then
passenger compartment fan, I could pull the voltage down into the 11's.
HOWEVER, the interesting thing is that blipping the gas didn't seem to
bring it up appreciably. I'll have to ponder this.
Again, thanks for your thoughts and ideas.
Bill
|
