No signal to the sub
 

I have an aftermarket sound system in my MINI installed by one of the P.O.s but just after I had fixed a battery charging issue, the sub is not making any noise. I admit, I messed around with it before I fixed the charging issue because I didn't want to drain the battery too fast while I was driving. Now that the battery charges just fine, the sub still doesn't bump. I know it's powered because I plug/unplug the signal cable from it can can hear the sub bump a little from the cable just moving in and out. I checked all the connections on the sub and the amp and they're all plugged in. I messed with the sub settings on the side of the box but no setting makes it bump anymore... It used to work, but I'm perplexed as to why it doesn't anymore.

Any ideas?

Fuses? A proper amp install would probably have an in-line fuse near the battery. Double check that it didn't blow. Also the amp should have one or more fuses or circuit breakers. That is where I'd look first.

You don't say what the battery charging issue was and the resolution to it, maybe something in that process is suspect.

Good point on the fuse there... I do see a blue LED light on the sub lit up, but I'll check the fuse that's next to the battery today. The charging issue was what I thought a faulty voltage regulator within my alternator but ended up only being an issue with the engine ground wire not being fastened properly at one end.

Maybe the woofer died, check if you have continuity across the two speaker inputs.