It's been a while since I posted anything mainly 'cause my truck has been running fine. Working with a problem now that has me confused. Any help would greatly be appreciated, THANKS.

My 2002 Chevrolet Silverado Duramax (LB7) has been running great for the last two years, still less than 45000 mile on it. Since I don't drive it a lot it sits in a garage with trickle chargers on the batteries to keep them fresh. A couple of days ago I tried to start it up and all I got was a clicking sound. I looked at the guages on the dashboard and NONE seemed to move which seemed odd. I figuared the batteries were dead, so I put them on a charger to charge up. After both batteries were charged the truck started and I drove to Autozone to have it checked. The tech said one battery was dead and the other was OK. I repleaced the bad battery and the truck seemed to start and run fine, but here is the problem.
When I put the key in the ignition and just as I start the truck the alt. gauge read just under halfway between low and high ( forgot what the numbers are) and after running for a couple of minutes jumps up to just past halfway on the guage. It has never done this before. Any ideas?? I am NOT getting any other indications that anything else is wrong.
Thanks.

Joe

So right after the battery change the volt gauge was pointing at the first mark or say a 1/4 of the way up the gauge and then after driving it moved up to 1/2 way up the gauge? Am I understanding that right?

The volt gauge should typicaly run about dead center or maybe a little above, the alternator should always be charging slightly, its when it drops way down that you have a issue.

When you change the battery you should do both.
Even though one is good, it will pull power from the fresh battery and eventually can kill it.

Yes,
Started about a 1/4 of the way up, then after a couple of minutes it move to just over 1/2 and stays there. No problems starting or running just concerned 'cause it has never done this before unless I never noticed it...

Joe

Sounds ok to me, All my vehicles have always ran right at the 1/2 mark which depending on the vehicle is usually right at 13 volts one side or the other. Automotive electronics are a 12 volt system and usually when the vehicle is running the alt. is making enough power to both run all of your vehicles electrical functions plus charge the battery.


Like I said, if its running high its charging your batteries, if its running low then your loosing power someplace (bad alt.) and your running soley on battery power and better get somplace quick.