Didn't really know where to post this,but since it all started with tryin' to remedy a poor heating problem via blower motor replacement, here goes: '69 Chev p/u never had great heat in winter since the day I bought it (1997).I decided it is either a worn out blower motor, or a clogged heater core, or both.Decided since the truck is 38 yrs old to replace both. Pulled the heater box off the firewall,took it down to the basement to remove old parts and clean it up,and lo-n-behold (!!!! ) some rodents decided this would be a great place to set up camp!!!!
Now I'm wonderin'......the truck's been sittin' in the woods for 5 yrs....the heater box was packed solid with decomposed leaves,pine needles,shreded paper,and foam rubber,from the bench seat I suppose. I tell ya,these mice were serious about tryin' to stay warm! My dilemma is, since the truck hasn't been moved in many yrs....could this be the original source of my poor heat???Could this nest have exsisted prior to when I bought the truck?? Has anyone out there experienced anything like this before?? I ask these stupid questions because now I'm wondering if I need to pull the box from inside the cab to check it.I hate doing things that weren't part of my original plans....not to mention,I just plain don't have time to mess with it.

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.

had the same situation with a '65 mustang. the first winter nearly froze to death, when i lived in kentucky!

removed the heater core, removed several generations of rat nests, cleaned it all with a clorox solution, then installed new core. for several winters thereafter, i was warm as toast!

Thanks for the replies guys, I did find mouse droppings in there as well,and there was also a nest constructed of similar material in the glove box,so I'm gonna assume that all this was done sometime in the last couple of yrs.Oh yeah....a tip for y'all...don't leave any valuable papers in your glovebox during any long term outdoor storage. I had the maintainence records (oil changes,routine service)in my glovebox,and it became "bedding" for the mouse hotel.Those records were my documentation that the odometer reading is "original miles".Oh well,live and learn.I will try your idea,I will empty the shop vac before trying to get anything out from inside the cab so I can tell just how much may be in there...already scrubbed the box on firewall side with disinfectant. God's blessings to you,

I know a guy who has had so much rodent damage to customer vehicles in his shop the IRS actually let him write off food and vet bills for his "shop cat" kind of silly I know.

Good story.

Run some water through the core to make sure It's clear & try the motor on the bench before installing, just to be sure.

I just went through the same thing with my van by leaving the engine cover off.

Good luck.