Q: We just putting in a brand new battery and alternator and last for the week battery now it won't hold a charge

Several issue may be causing the battery to not charge or not hold a charge. The first and easiest step is to trace the wiring circuit involved with the starting system, and visually inspect it for any physical damage.

All of the connections need to be clean, dry, and tight. The conduit needs to be flawless and with no breaks or cracks. These flaws can allow moisture in and corrosion to form. A bad connection may have been jostled enough during installation to make a connection temporarily.

As long as the battery and the alternator were replaced together, the issues are likely wiring-related. Otherwise you may be looking at a bad alternator ruining the new battery.

If the starting system seems flawless, you may be experiencing a parasitic draw on the battery. These can be caused by aftermarket parts, radios, security systems, or any component that requires a memory for a setting. You can likely test for a draw with a proper scan tool.