Date registered: Feb 2010
Vehicle: 1972 280SEL daily driver. 904 Dark Blue with cognac interior. euro 4.5 engine
Location: Williamsburg, VA
Mentioned: 3 Post(s)
Quoted: 50 Post(s)
Per your diagram, the W114 aux fan is just like my W108 fan. It only comes on if either the coolant temperature is over 212F or the refrigerant temperature leaving the condenser is over 52C (125F). My aux fan never runs unless I'm stopped in traffic for more than ten minutes in hot weather because my manual fan keeps both of those temperatures below the setpoint. I think your aux fan may be ok if it runs when you connect it direct.
As for the clutch and blower not working, the common link in that chain is the changeover switch.