I recently had my 97 9000 Aero in for repair at my excellent local repair
shop. I had them replace the ignition switch in the steering column. While
there, I asked them to check the electrical system generally because of
something I'd noticed. As I'd drive down the road, I noticed that the
voltage on the dashboard indicator would go up and down. Anywhere from 11
volts to 14.2, usually up around 14 where it belongs. They found that the
alternator was putting out considerably less than the correct amount so I
had them replace it. I still have some fluctuation in the reading on the
gauge but much less than I used to have. But, as I drive along, I do notice
a dimming of the headlights from time to time. No new load (like an a/c
compressor) kicking in, just driving down the road. The lights come back up
to normal brightness in a few seconds. The shop is aware that the voltage
still isn't right but none of us are sure where to check next. The battery
is about two years old, on a 60 month Interstate battery.

Anyone have an idea on what might be causing this fluctuation in the
voltage?

Thanks.