Battery not charging
 

I just bought a new battery. After two weeks it was dead. I re-charged it and it lasted two days. Am I right to assume my alternator needs to be replaced

With the engine running, put a multi-meter on the battery and check the reading. Should be upwards of 14 volts, if it is charging. Or take the car to AutoZone, etc. and they can tell you if it's charging. It may just need a new voltage regulator. OEM alternators are pricey. This is a DIY project with the right tools and patience. Pulling the alternator is a bit finicky. Good luck.

Also thinking it's likely the voltage regulator. Replaced mine last fall and it cured the low alternator output.

Most likely the voltage regulator, but you need to pull the alt either way. You can then have it bench tested. As mentioned, check your alt output. You could just have a bad battery as well, it happens. Pulling the alt isn’t the most fun job... it can be a real PITA in fact... plenty of info out there on how to do it.

I tested it with a OBD ll scanner and it read 'Low Voltage'

1. Since you just replaced your battery, make sure connections are tight. Wiggle both cables to be sure.

2. If you don't have a meter or understand charging system, go to the Auto store of your choice and ask them to test your charging system (best) or battery.

The diagnostics aren't hard or expensive and is easy to isolate issue in most cases.