Toyota Repair: 93 Corolla (5 speed) A/C blows foul air, humid weather, t drain

Question
The car started blowing foul smelling air around 120,000 miles. It now has 150,000 miles. This somehow occurs only when I use the heater during a humid weather. It is not as bad when I cool down the car during a humid weather in the summer. First I thought it was a small dead animal stuck inside the engine compartment.

Please help!

Thanks,
Ronnel

Answer
That could still be the case but it could also be that the evaporator drain hose is clogged and the condensed water can't drain which causes fungus/mold to form inside the housing, make sure the drain tube is not obstructed water drains out on to the ground when using the A/C.