Battery dies after new stereo installed 97 Rodeo

[Kayleigh]

The day after I had car toys install a new stereo the battery died in my Rodeo. I purchased a new battery, as I recently purchased the vehicle (less than 3 weeks prior) and wasn't sure how old it (the battery) was.

After the new battery was installed, it ran right around 12 volts, never getting higher than 13. (mid-range battery, not cheapest one).

Last night it dipped down to 11 volts and had a hard time turning over, today it died again.

We were able to jump it, but it died again in an intersection. The Battery light NEVER came on.

My question is this, should I be cussing out car toys right about now for causing a short? or should I get the alternator checked out first? The previous owner claimed to have installed a new alternator just a few months ago, but didnt provide the paperwork to back this up.

Also, will an auto parts store be able to test the alternator with it still in the vehicle? or would I need to remove it first?

[Kayleigh]

Update, The problem was the alternator, installing a new one has resolved the issue (for now).