Depending on the year it could be easy or very difficult to get the blower motor out to inspect it. If its 94+ body style they arent so bad to remove. Three screws (phillips head or 8mm hex) and you should be able to weasel it down and out of the hole it resides in. Most times you'll find pieces of leaf or pine needles making noise, but occasionally its the blower motor bearing that is making the noise and you would have to replace if you cant oil it. (never tried oiling it)

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