Silverado Alternator not putting out proper volts - Already changed the alternator... - Page 6

someday31 · #76 03-10-2010, 08:42 PM

Truck is going back to the dealer....they agreed they missed something and are willing to look at it for free! I will let you guys know what they come up.

someday31 · #77 03-11-2010, 09:21 PM

Quote:

Originally Posted by someday31

Truck is going back to the dealer....they agreed they missed something and are willing to look at it for free! I will let you guys know what they come up.

So they came up with a supposed "fix"... they ran a wire from the alternator output back to that one free terminal on the wire harness that goes into the alternator. Ever heard of doing this...they said their was a tsb out about doing this?

rhandwor · #78 03-12-2010, 07:18 PM

According to my Alldata for a 2000 it says. "The S terminal maybe used to "sense" voltage at another location on the vehicle for voltage control. If the S terminal is not used the generator will use an integrated circuit in the regulator to "sense" voltage."
Maybe you had a bad voltage regulator. Does the repair work properly for your vehicle?

someday31 · #79 03-13-2010, 12:59 PM

Went to the alternator shop and he ran tests on my battery with the snap load tester, it failed the test...again! He said the battery went down to under 9 volts when doing the test, he said it should be 10 at the lowest during that test, he showed me a battery on another vehicle so I could see what its suppose to be.
So that thing the dealer did had no effect! What should I do???? I am out of ideas........

someday31 · #80 03-13-2010, 01:38 PM

Quote:

Originally Posted by someday31

Went to the alternator shop and he ran tests on my battery with the snap load tester, it failed the test...again! He said the battery went down to under 9 volts when doing the test, he said it should be 10 at the lowest during that test, he showed me a battery on another vehicle so I could see what its suppose to be.
So that thing the dealer did had no effect! What should I do???? I am out of ideas........

Could someone please goto an autozone or advanced auto parts for a load test and see what they get? I want to see if you get a good battery, full charge!

rhandwor · #81 03-13-2010, 03:06 PM

Quote:

Originally Posted by someday31

Went to the alternator shop and he ran tests on my battery with the snap load tester, it failed the test...again! He said the battery went down to under 9 volts when doing the test, he said it should be 10 at the lowest during that test, he showed me a battery on another vehicle so I could see what its suppose to be.
So that thing the dealer did had no effect! What should I do???? I am out of ideas........

Use a brush shaped like this for GM side terminals. Clean both sides good and hook up battery cables. Battery and cable I think this is your problem area.
http://www.autopart.com/tools/toolsmain/tool/T_3120.htm
I would borrow a battery charger if you don't have one or purchase a good one.
Charge the battery up completely then ask for a retest you may have a bad battery. I have my own load tester and my battery is working fine.
Not all batteries are fully charged when you purchase them. An alternator will maintain a battery but not always bring up a discharged battery.

someday31 · #82 03-13-2010, 03:45 PM

I do have a charger. I got another brand new battery under warranty, will charge the new battery and put that in and I have seen that terminal cleaner, will buy one. I will do all of this tomorrow morning and let you know what happens. I have already had the newest battery that is going in, load tested and it passed so I am sure it is a good battery! I hope another good cleaning does the trick! Thanks for getting back to me !

someday31 · #83 03-13-2010, 07:24 PM

I just realized that is for top post terminals, I have side ones so cant use that tool. I will still try cleaning them again though tomorrow.

someday31 · #84 03-15-2010, 09:28 PM

The dealer agreed to take my truck back for a 3rd time! They said this time they want it for a few days! Im not sure if I even trust them to figure anything out at this point and ruin something.

rhandwor · #85 03-16-2010, 11:09 AM

Quote:

Originally Posted by someday31

I just realized that is for top post terminals, I have side ones so cant use that tool. I will still try cleaning them again though tomorrow.

The picture on the link was for both. But you need a GM terminal cleaner. The round brush cleans around the bolt. You can use a pocket knife and scrape the side of the battery or some emery paper.
Surely the dealer can check out a alternator problem.

DJ JEFF · #86 05-12-2010, 05:23 PM

The End!

No fix? I read through this whole 6 pages and didn't get to see what the fix is?

someday31 · #87 05-12-2010, 08:06 PM

I gave up! Never got it fixed. Truck starts/runs, but fails load tests. Any suggestions...experiencing the same thing?

JimPratz · #88 08-10-2013, 04:09 PM

I wondered if anyone ever figured out an answer to this old this (new to the forums), my truck is doing the same exact thing (2008 Silverado, bought brand new, replaced alternator also with new GM AC DELCO (not rebuilt) and have gone thru literally 5 NEW BATTERIES... )... I've had the truck to the GM dealer 4 times for the issue and even over night and no answers, they have many excuses and like to say it's normal but it in fact IS NOT NORMAL, my truck used to always charge at around 13.6 to 14.2, I have NO after market accessories, only 66k miles on truck, any ideas...?? Everytime I have taken it to the GM dealer they say it checks out fine, same with Advanced Auto with their meters...

I did notice this however, when the voltage drops while dropping (goes down as low as 11.8v, but usually only goes down to 12.4v.... if it does this while driving, and I put in neutral, then restart truck it goes back up to 13.4v - 14.4v and stays there for quite a while, until next restart...

I'm in the process of replacing the 175AMP Megafuse but this is my last check I know of... (I am doubtful its the cause however)...

Thanks for everyone's help - Jim.

rhandwor · #89 08-10-2013, 05:57 PM

If the dealer don't want to help you have a wiring problem. You can go to an alternator rebuilder and have a self excited regulator installed. Make sure the alternator is installed according to the rebuilders instructions.
Some of the newer trucks may need a new computer. On my 2000 the instrument cluster may need pulled and repaired. or a bulb replaced.
They need a wiring diagram to check and repair the exciter for the alternator.
I would try another dealer.

j cAT · #90 08-10-2013, 06:10 PM

you have a 2008 silverado this is quite a bit different than the 1999-2006 models.

some of these newer body style silverado trucks have MPG enhancer PCM in them. with this the voltage will drop down to 12 volts then shoot up to 14 volts. this is to according to GM increase the MPG.

I would not worry about it . you had it checked. and If the dealership said this is normal then you got one of these type PCM computers.

I guess you could put a self excitation alternator . this would always put out power with the proper amount as the demand varys it would bypass the PCM. not sure how it would work with the alternator failure light though.

did the dealership say it is normal to have 5 batteries replaced. even if the alternator was not putting out power all the time the batteries should not get damaged. you had all these batteries load tested and they indicated bad cells or what ?

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