Check the Heater blower regualtor which is the aluminum piece under the motor itself. It has a bunch of aluminum rods that stick out. We call it a porcupine.
These fail all the time ! =)
1994 E500 (MY SUNDAY DRIVER)
1993 190E SPORTLINE LE W/ M104 SWAP
2000 BMW 528I (WIFEY'S CAR)
"Excuses are crutches for the unfounded."