Let me piggie back on this one. I've noticed the last few days that my ammeter shows fairly strong charge like midway between midpoint and the + for maybe 10 miles of fwy driving before coming back to midpoint. It used to charge to about that for a minute or 2 after startup. Starts fine though and no other indications of something wrong. Is this an indication the battery is getting pretty weak?

40 Chevy 1/2 ton