W126 Weak Blower Motor - CCU?
 

Hey guys, I'm helping a friend out and fixing his '91 420sel. The blower motor is weak and the low,auto,hi buttons don't do anything. I'm getting 12v constanly from the red reg wire to blower, doesn't change with any combination of buttons pressed. Obviously I searched and found the reg is the most common issue, but i also read about the ccu having bad solder joints.

The blower will run on high if I jump it, so I know its good.

Any insight?

Blower regulator.

Yeah I ended up testing the ccu with a MM at the regulator plug. It worked fine so I headed to the junk yards and ended up with 5 regulators for $4. Blower works great now, just blows hot air though :( hopefully its just low on freon.

The aux fans aren't getting power either, does anyone know the relay configuration?