I could not reply to your email - AOL says docdav130 is not valid, but here is what I would have said.
There is no "blower regulator" that I'm aware of. There is a relay behind the glove box, and there is a set of resistors near the motor. If the blower is working on DEF then the relay is OK.
The speed of the motor is controlled by the "system" depending on the desired/actual temperature and the function selected on the control panel.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe