Battery in suburban was dead or so we thought after only 6 months old. Not un-common I guess. The battery light would come on, after driving around the block, it would show charged and light would go off. Dash guage would show 13.5v. I replaced the battery with one from Kragen. Their best one (not red top). Now, I test the battery it shows 12.7v. I start it, it takes 5 seconds then shows 14.7v. But, guages moves slow. No battery light now. The tahoe, shows 12.7v, once started it quickly jumps to 13.5v. No issue with tahoe. Why does the suburban take a few seconds longer? Why did battery light come on with old battery? Thanks guys.

2002 Suburban
2003 Tahoe

 

Welcome to the forum,

I would have the charging system checked out, if you pull the alternator and take it to a good shop they can bench check it... some dealerships may perform a charging system check out for you also at no or minimal cost....

If that all checks out you may have a parasitic draw going on... check all vanity mirror lights, glove box lights, make sure no accessories are plugged into power outlets... check aftermarket add-ons like amps or video equipment...

 

Both the sub and tahoe show 12.7 on the volt meter before start. So, I assume no loss/draw over night.

It's the slow charge up to 14.7v after started I am curious about. It's about 5 sec slower than the tahoe.

 

I'd have the charging system checked out... as a weekend sanity check you could try swapping the batteries between the Suburban and the Tahoe...

 

I had it checked out by two shops. Both said nothing wrong with batt or alt. I did replace the batt anyways. Didn't cure it. $100+ dollars blown there. lol

 

What I see in Haynes is the body control module controls the field voltage to the alternator, same as the old voltage regulator. To me electronics work or don't work. Why it's doing this I don't know.

 

Ya, it has my head spinning. Not sure which is worse? My wife saying each morning "it did it again" and not be able to solve it.

 

If its going dead something is draining it somewhere...
I'd try pulling a few of the larger relays and fuses a few at a time and see if you can isolate it that way....

 

It never actually dies. Old battery would show the battery light come on. But, still start. New battery doesn't show light on.

Just trying to give facts to help narrow it down

 

So the new battery seems to be performing correctly, but you were questioning the fact that the 6 mo old battery was causing the Batt light to come on correct?
Yeah it could have a been a dud...but keep an eye on it, if something is draining it, the battery will eventually loose the battle and won't keep a charge if discharged too much too often....