Toyota Repair: Smells, rodent infestation, cabin air filter

Question
I have a 2002 Toyota Sienna.  It always has had a musty smell the Hear or Air is turned on. After not driving the van on a regular basis the odor has become almost unbearable.  What can I do to try to clean the ventilation system?

Answer
There are a couple of reasons for this, first, the a/c evaporator drain hose may be clogged causing the condensation to collect inside the evaporator housing and then developing mold and midew, make sure the evaporator is draining, you can check it by turning on the a/c then leave it on and wait until you see water dripping from under the car, this may take 15-20 minutes, if after about 30 minutes there is no water exiting the drain tube there is a problem an it is clogged up possibly with leaves or other debris.
The other cause may be that rodents have gotten into the air ducting and possibly have died in there, remove the glove box and remove the cabin air filter for inspection, to look for any signs of rodent infestation.