The mechanically driven fan on the 190E 2.6 is a thermo-viscous drive. It keys off radiator exit air temperature, but the clutch typically tightens at about 100C coolant temp (as displayed on your IP gage), and at this point you will probably hear "fan roar" at 2000 revs.

The early 2.3s have an electromechanical clutch that actuates the mechanical fan. I'm not sure if later 2.3s are the same or viscous.

The electric fans on your car should engage at high speed at about 105C coolant temp, and when the A/C is on they will engage at low speed periodically in low speed driving based on A/C cooling demand.

I recently posted a way to test all the fan functions.

Duke