replaced alternator , now ive got lower voltage 1996 k1500 5.7L

[T1najero]

i replaced my delphi alternator because its been bouncing with my turn signal for a little while now but it stayed at 14 volts and never dropped below 13. i bought a AC Delco from summit and watched some YT vids ( my first time replacing an alternator ) after installation the gauge showed 12 volts with battery light and almost touching the orange zone. went to AutoZone to have them check it and they said the alternator didn't pass and was bad. bought a Duralast and still low voltage, but said now the battery was bad. went to oreilly's to see if the battery was under warranty. it wasnt and i bought the same battery. left for work and installed there. still low voltage.. what do i do now ??? am i missing something ?? im lost and on my last legs. and the last resort is going to a shop. even though theyll most likely charge me lots..

thanks in advance, much appreciated..

 

[DerekTheGreat]

Why did you replace the old alternator??? Sounds like it was working fine. Don't fix what isn't broken.

The gauge on the dash is not accurate, it's more of a reference. Mine lags when the signals are used too, never known an older vehicle whose volt meter didn't do that. However, that doesn't mean the alternator is bad or that you don't have crusty wiring connections and what not.. The thing to do is to measure the output at the battery with a volt meter, engine running vs engine off. With the engine off, voltage measured at the battery should be 12.x for a good battery. When it's running, should be higher than that, ideally 14 and some change. That's of course application dependent.

 

[South VA]

i replaced my delphi alternator because its been bouncing with my turn signal for a little while now but it stayed at 14 volts and never dropped below 13. i bought a AC Delco from summit and watched some YT vids ( my first time replacing an alternator ) after installation the gauge showed 12 volts with battery light and almost touching the orange zone. went to AutoZone to have them check it and they said the alternator didn't pass and was bad. bought a Duralast and still low voltage, but said now the battery was bad. went to oreilly's to see if the battery was under warranty. it wasnt and i bought the same battery. left for work and installed there. still low voltage.. what do i do now ??? am i missing something ?? im lost and on my last legs. and the last resort is going to a shop. even though theyll most likely charge me lots..

thanks in advance, much appreciated..

Welcome to the forum!

Not sure which vehicle you have - it's really helpful if you'll put that in your post, as GMT400s vary somewhat with the model year. EDIT: it's in the title of the post! Doh.

My experience was similar to yours, in that I wound up with a new alternator when the old one supposedly failed. Like yours, the gauge needle would often (but not always) bounce with the turn indicators, and would read low.

I also replaced my battery, which helped but did not completely cure the problem.

Turned out that I had a bad ground. The ground wire running from the negative battery terminal to the inner fender liner had a weak terminal end that eventually broke when I removed the bolt to clean up the connection. Once I fixed that my charging problem was resolved.

Good luck with your search.

 

[0xDEADBEEF]

Besides the obvious stuff like making sure everything that was disconnected was reconnected, was the belt tensioner strong? Belt slip can cause charging issues. Also make sure the terminals on the battery are good and tight.

 

[Caman96]

Save that Delco.

 

[Schurkey]

With the engine off, voltage measured at the battery should be 12.6--12.7 for a good battery. When it's running, should be higher than that, ideally 14 and some change.

FIFY. 12.2 is HALF-DEAD. 12.0 is dead.




TODAY--THIS MORNING: Friends of friends have had their '97 GMC Sonoma V6 Vortec parked in the driveway since last fall. I was told it needed an alternator. I get an alternator from the Treasure Yard for them about October, after the first snow of the season...but they live 90+ miles from me round-trip, and they won't take it home because nobody there can install an alternator. Of course the battery is totally dead, and none of them can remove the battery before freezing weather, so now the battery is probably ruined from freezing.

So I drive up there, with the alternator, and when I open the hood I see that the alternator on the engine looks beautiful including the "Rebuilt in Mexico" paper tag on the thing.

So I grab the battery cables at the battery. Positive is nice 'n' tight. Negative flops around like a wounded guppy.

These folks--five drivers in the family, four out of five cars including this Sonoma down for the count and the Ford Focus shakes like it's having an org_asm at highway speed, and the check-engine light has been on for the two years I've known them. This Sonoma--probably the second-best vehicle in their fleet--has been sidelined for four or five months because THE BATTERY CABLE IS LOOSE and the battery got discharged. And then the discharged battery froze.

At this point I can't say that the alternator is good or bad, until we get the battery thawed and charged, and start the engine. But I have my suspicions. I left my battery charger with them.

 

[GoToGuy]

Anything indicated electrical instrument wise, is more a notice of something to be checked, diagnost. Remember " trust but verify ".
Your troubleshooting approach has to adapt to a vehicle whose status is not a new vehicle anymore. Besides the usual things break skill, you have the " aged vehicle " issues that now happen to all.
And yes, my volts gauge varies a little with turn signal operating. It's normal , extra load , long wire travel, load varies so alt' plays " catch up".
Learn basic DC electric, do basic troubleshooting, don't buy parts you don't need. Not all parts stores are skilled at basics, there test equipment may not be accurate. When installing new alternator ensure you have fully charged battery. Do the basics, save your cash for goodies you want.

 

[Deancr11]

FIFY. 12.2 is HALF-DEAD. 12.0 is dead.




TODAY--THIS MORNING: Friends of friends have had their '97 GMC Sonoma V6 Vortec parked in the driveway since last fall. I was told it needed an alternator. I get an alternator from the Treasure Yard for them about October, after the first snow of the season...but they live 90+ miles from me round-trip, and they won't take it home because nobody there can install an alternator. Of course the battery is totally dead, and none of them can remove the battery before freezing weather, so now the battery is probably ruined from freezing.

So I drive up there, with the alternator, and when I open the hood I see that the alternator on the engine looks beautiful including the "Rebuilt in Mexico" paper tag on the thing.

So I grab the battery cables at the battery. Positive is nice 'n' tight. Negative flops around like a wounded guppy.

These folks--five drivers in the family, four out of five cars including this Sonoma down for the count and the Ford Focus shakes like it's having an org_asm at highway speed, and the check-engine light has been on for the two years I've known them. This Sonoma--probably the second-best vehicle in their fleet--has been sidelined for four or five months because THE BATTERY CABLE IS LOOSE and the battery got discharged. And then the discharged battery froze.

At this point I can't say that the alternator is good or bad, until we get the battery thawed and charged, and start the engine. But I have my suspicions. I left my battery charger with them.

FIFY. 12.2 is HALF-DEAD. 12.0 is dead.




TODAY--THIS MORNING: Friends of friends have had their '97 GMC Sonoma V6 Vortec parked in the driveway since last fall. I was told it needed an alternator. I get an alternator from the Treasure Yard for them about October, after the first snow of the season...but they live 90+ miles from me round-trip, and they won't take it home because nobody there can install an alternator. Of course the battery is totally dead, and none of them can remove the battery before freezing weather, so now the battery is probably ruined from freezing.

So I drive up there, with the alternator, and when I open the hood I see that the alternator on the engine looks beautiful including the "Rebuilt in Mexico" paper tag on the thing.

So I grab the battery cables at the battery. Positive is nice 'n' tight. Negative flops around like a wounded guppy.

These folks--five drivers in the family, four out of five cars including this Sonoma down for the count and the Ford Focus shakes like it's having an org_asm at highway speed, and the check-engine light has been on for the two years I've known them. This Sonoma--probably the second-best vehicle in their fleet--has been sidelined for four or five months because THE BATTERY CABLE IS LOOSE and the battery got discharged. And then the discharged battery froze.

At this point I can't say that the alternator is good or bad, until we get the battery thawed and charged, and start the engine. But I have my suspicions. I left my battery charger with them.

There's just a special group of people running around any more that scare the hell out of me. I do believe you should check your grounds and connections before you do much more

 

[AuroraGirl]

OP states problem in title

The problem was he changed his alternator. OP, clean the bracket where your alt mounts, clean the engine, body, etc grounds. there should be one for the engine dedicated to the battery. there should be one from the engine to the firewall(or somewhere body wise, like fender etc.

There should be a frame to body like to the core support, fender, firewall. There should also be solid connections on all these I listed, and then the battery should be solid too.


You, oP, got a new battery, thats good. Do the other stuff I said and i think youll have nothing else going wrong

 

[jd33173]

Anything indicated electrical instrument wise, is more a notice of something to be checked, diagnost. Remember " trust but verify ".
Your troubleshooting approach has to adapt to a vehicle whose status is not a new vehicle anymore. Besides the usual things break skill, you have the " aged vehicle " issues that now happen to all.
And yes, my volts gauge varies a little with turn signal operating. It's normal , extra load , long wire travel, load varies so alt' plays " catch up".
Learn basic DC electric, do basic troubleshooting, don't buy parts you don't need. Not all parts stores are skilled at basics, there test equipment may not be accurate. When installing new alternator ensure you have fully charged battery. Do the basics, save your cash for goodies you want.

Yep, charge up that battery before you fire up the alternator to give your alternator the best chance. Checking grounds also massively important