There's also a drainage line back there for the AC drainage line. Sometimes it clogs from leaves or dirt and just needs to be cleaned. This happened to me a few months ago on my '15. Subaru will know what you mean
I caught the water running down from behind my glove box and was like what the f. It hadn't rained but I ran my AC all summer long and each time I ran it, a couple hours later there would be a trickle or a soaking
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