stick an air freshener in the interior vent
Unplug clogged evaporator drain plug.
you wash it????
Vinegar
Go to a professional cleaning supplier and ask them. They have the knowledge and the products to do the job.
"The musty smell of the attic filled my nostrils" BWHAHAHAHAHAHAH
The first step to getting a musty smell out of a closed up house is to open the windows. You will also want to burn some candles. Spraying Lysol will also help get rid of the musty smell.
The Air Conditioner drainage hose on the 2004 Impala is located in the passenger side firewall. A clog can cause a musty smell, or worse.
The musty smell that Brian notices when he wakes up is caused by the dampness and mold growth in the shelter. The combination of moisture and lack of ventilation can create a musty odor.
Bleach
It is probably mold growing inside the air conditioner, which blows out into the room. This is fairly common, especially if the humidity is relatively high in your area. If your carpets are damp, they too can harbor smelly mold.
wash everything and febreze...
try using an air freshener