Nissan Repair: Air conditioning/heating, nissan pathfinder, blower unit

Question
I am experiencing a musty smell for a short time upon starting my '94 Nissan Pathfinder's air conditioner (panel blowers) and the same smell continuously while running the heater (defrosters). What could be causing this problem? What are your suggestions? Do I need to clean the fan/blower unit and or air ducts?  

Answer
Carren,

The airconditioner evaporator gets dirt and mold on it from being wet all the time.  It smells until the system cools down.  You can purchase a cleaner solution that can be sprayed in the intake vent under the dash to clear out the smell.  Also, check to see that the water drain is working properly.  it is located on the firewall on the passenger side of the engine compartment and very low.  Look for a black rubber hose that sticks out of the firewall about two inches.  Check to see if it is blocked and not letting all the water out.