1992 400SE poor heat bad smell

[Maleic]

My car stinks - really. I know this sounds funny but at about the same the heater started to function poorly the car started to smell like something crawled inside and died. I keep my are very clean and have looked for something left inside that spoiled - that's not it.

The heater produces heat, but the blower isn't working very effectively. Is is possible that a small critter has gotten into the heating system somewhere and is clogging it up? Or does this sould like something else

Thank you for your help