Oh,yeah,squirrells,mice,chipmumks and such will find many places to live in your truck especially if it sat unused for awhile. I've been pulling out nut shells and nest webs since I bought my '50 a year ago!Try vacuuming with an extension wand into your heater box and if you can run your fingers around inside to feel for stuff you can pull out or at least loosen up to vacuum.
