The fans are triggered by a temperature switch on the receiver dryer to cycle with refrigerant temperature. There's also a switch in the engine head to switch the fans on if the engine overheats. If the fans are disconnected, the A/C will not work very well at low speeds due to excessively high head pressure from lack of airflow. Engine temp is maintained by the engine driven fan. The viscous fan clutch may be slipping excessively and causing poor cooling performance.

The center vents are vacuum operated, controlled by the pushbutton unit. If nothing is working, I'd look to see if you have a blown fuse to the A/C system. If the aspirator motor seizes and lets the smoke out, it can take the fuse out (been there, done that). A seized or shorted auxiliary coolant pump can also cause problems.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)