Hello again,
Okay, that's good. It'll take care of the jumper cables being hooked up backwards, Now on to the original problem. Can you take a voltage reading across the battery terminals with a Digital Multi-meter [DMM] for me, please? If you are unfamiliar with how to use a DMM, here is a link below explaining what to do:
https://www.2carpros.com/articles/how-to-use-a-voltmeter
Please get back to us with what you find out, we can go from there, if needed.
Thanks,
Alex
2CarPros
Thursday, November 7th, 2019 AT 2:37 PM