My heater went out in the fall, I never had the time or money to start on it till now. I checked all of the fuses, including the strip fuse, no luck. Then I got to the blower motor, but it turned out the motor was just fine. I figured "must be the regulator", bought a used regulator... and still I had no power to the blower motor. Finally took it in to a Mercedes mechanic, he checked out all of the wiring and connections and then replaced the wiring that leads up to the strip fuse. I didn't even know it could go bad, but this car doesn't surprise me anymore at all.

Just wanted to add another possible solution to all of "W124 failed heater" threads.

And if anyone wants a used regulator, mine is up for sale in the classifieds.

oooo! I will look at that tomorrow... my blower motor has not been activating. Heat comes out but just no fan to blow it... unless I go over a speed bump and it suddenly shoots on... LOL! somewhere there is a short or the fuse is going bad and the little bump gets the contacts good enough... I am going to check it all tomorrow INCLUDING the wire leading up to the inline fuse