Caroline wrote:
>
> 1991 Civic LX 4-door sedan, 1.5 Liter, manual transmission, no air
> conditioning, 156k miles, here.
>
> Voltage at the battery terminals when the car is
> -- idling = about 12.7 volts
> -- stopped, ignition off, also about 12.7 volts
>
> In February, these numbers were 14.5 volts and 12. 4 volts.
>
> Internet sources say a voltage when the car is idling of around 14
> volts or so indicates a properly operating charging system. So something
> is wrong, IMO.
>
> I put in a new battery (Interstate) today, replacing the old one
> (4-years-old; Diehard; wrong climate design as I moved from up North
> to the Southwest in the past year?). The voltages above didn't change.
>
> The car is on its second alternator (OEM). This 2nd alternator is 5
> years and 50k miles old.
>
> I installed a new alternator belt in June. I originally had the belt too
> loose, as indicated by a squeal at cold startup. I tightened it and the
> squeal stopped. Unfortunately I did not at this time check the battery
> terminal voltage.
>
> I did shake out quite a lot of white powder (indicating some corrosion)
> from the battery's positive terminal's cable connector while changing the
> batteries.

If my memory serves me correctly, you may want to check the battery cables
for a voltage drop. Can you measure a large voltage drop (high resistance),
i.e., more than 0.3-0.5V, across the battery cable? If so, then it may need
to be replaced.

Note: To measure a voltage drop connect the + lead of your DVOM to the +
battery terminal and the - DVOM lead to the other end of the wire at its
connector.

Eric