Alternator and battery issue
 

Folks, I have a 2005 6 cylinder Tribute.

I recently had the infamous alternator replaced with a new ACDelco alternator, for the reason that, a) battery light was on, b) car would click when the key was turned, c) tested the battery when the car was off and it read 12.35 volts.

I cleaned battery terminals, checked the connections to the alternator for corrosion (none detected), and then set about trickle charging the battery. After a day, started the car and the multimeter read just over 12.35, so I figured...alternator. Took the thing to a shop, and had them replace the alt with the new AC that I bought separately (thus avoiding the 200% markup) which they were ok with. They allegedly tested the connections, agreed that it was the alternator, swapped it out...with reportedly much swearing.

Car was running fine last two days, this morning, the thing won't turn over. Battery is once again reading "12.35" volts. What am I missing here? Trickle charging again, so I can test it while running....but I think I am missing something.

Thoughts?

Thanks!

So you had a flat battery, trickle charged for a day and it was still flat (so it can't be the altenator if it won't trickle charge...), replaced the altenator and now its flat again?

If the battery connections really are all clean, tight and good electrically then I'd say it sounds like a problem cell in the battery not accepting charge - may have been the problem all along unfortunately. On a good battery 12.35V is plenty to start an engine.

Nooo, but almost.

Truck won't start. So I tested the battery with the multimeter, 12.35v. Clicks when attempted start. So, I trickle charge over night. Next morning truck starts. I test the battery again, 12.85. I figure alternator, take it to shop, alt replaced.

Day and half after alt change, no problem. Next morning, won't start...battery still reading 12.35. Put it back on charger, said it was charged in less than an hour? Turned over though...now reading while running is 14.2v. Which makes me think the alternator is working, so it must be the battery?

14.2V is definitely alt working, sounds like the batt isn't taking much charge to me so I'd swap that out with a known good one (doesn't have to be new at this stage), then replace if the problem moves with the battery.

How old is the battery? I replace my auto battery every 2 years and motorcycle battery every 3 years.