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: 1999 4Runner SR5 V6 2WD ~310,000 miles
Location: Dallas TX area

Any thoughts would be greatly appreciated!