Battery Problem

2005 Silverado 2500HD 6.0 with 68,000 miles. Battery will not hold a charge. Replaced the battery, then the alternator, still won't hold a charge. Removing the negative terminal and placing the voltmeter between the terminal and the battery gives a reading of 3.0 mv. Should be okay. Does anyone have any ideas what may be causing me grief?

2005 Silverado 2500HD 6.0 with 68,000 miles. Battery will not hold a charge. Replaced the battery, then the alternator, still won't hold a charge. Removing the negative terminal and placing the voltmeter between the terminal and the battery gives a reading of 3.0 mv. Should be okay. Does anyone have any ideas what may be causing me grief?

you need to place a current reading meter between the ground battery terminal and ground connection to battery..not a voltmeter..

set to 10amps then drop to a point where you get a reading should be less than 250ma...ideal is 20ma....the computer always draws current from battery...

If it reads higher than the 250ma start removing fuses...start with non OEM equiptment ,this is usually the cause ...then disconnect the alternator...new means nothing....

Thanks for setting me straight j cAT. Using the load setting on my multimeter, I pulled fuses and found the load coming from the 20a accessory fuse. The culprit - XM Roady 2 transformer plugged into the auxillary cigarette lighter. As you said, "check add on items first".