Yup. Dog hair will definitively get in there if you use MAX A/C, since MAX is A/C + recirc. The return register is under the passenger dash, and is a straight shot into the blower motor. Actually, besides the A/C evaporator, dog hair hair could easily wrap around the squirrel cage. The heater core is relatively protected, since all the air goes through the evaporator first. I was surprised how many pine needles were in my evaporator, considering I only park under evergreens when I'm camped. I don't have any at my house. A small vacuum hose can be stuck through the blower opening to vacuum that out. While the blower is out, you can inspect the motor itself though the vent-port on the bottom. My brushes were simply worn out. Once the battery out, it might not be too much trouble to crack open the clamshell plenum holding the evaporator, but I was able to get enough debris out, so I didn't try.
2000 E450 dually V10 wagon