The replacement of the blower motor isn't too bad. After removing the small trim strip at the top edge of the knee bolster, and then removing the knee bolster itself (passenger side), there are just a couple of bolts to let the motor housing open up, and then to drop down the motor and "squirrel cage" assembly. I didn't see a good way to open up the motor, so you might have to buy a replacement motor.

This will sound "kludgey", but when my motor started getting intermittent (not running at all, or running for brief periods), I found that inserting a couple of small shims below the brush assembly served to make it run again. This is hard to describe, but there was a small gap in the plastic housing around the brushes (below the brushes, when the motor is oriented as it is in the car). I used some small plastic screw anchors I had laying around, simply pressed into this gap. My theory as to why it helped is that it possibly raised the brushes slightly to a less worn area of the armature. All I know is that it worked, and it cost nothing. If the motor starts going bad down the road, I'll decide to replace it then. In the meantime, it has now been working fine for a couple of months.

rschleicher
1991 420SEL - 171,000 miles