Replaced car battery, now A/C has weird smell

I had Walmart replace my car battery about 3 weeks ago, and ever since, there is a strong smell coming from the A/C even when I turn it off, but much more so when it's on either blowing hot or cold, doesn't matter.

Hard to describe the smell, but I don't think it's mold or mildew. Perhaps an "electrical" or "burning" smell?

I've replaced the battery in this vehicle many times (including same model battery top rated by Consumer Reports at this same Walmart 6 years ago) never had a problem like this!

What on earth could be going on?

Vehicle listed above SR5 model.

Any thoughts would be greatly appreciated!