It could be clogged. Take something like a zip tied and see if you can push it though. Be prepared for a gush of crap to shoot out if it is clogged bad.
Some have had the cowl drain (like posted in post #35) get clogged up and cause water to build up in the cowl area. From my understanding it overflows and pours into where the blower motor fan is. I guess it could work it's way around to where it would drain out of the HVAC box drain in the fire wall.
Here's how I did mine.
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Thanks for this. Much appreciated. Before I rip cowl off will check this first.