The Mercedes EPC gives a good cut-away view of that area. If the blower motor is accessable (I have NO idea on a 107; is on a 126), seems like you might be able to use a magnet probe "upwards" and "rearwards". Good luck.
Seems from the EPC pictures that the blower is forward of where your knife would be.
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)