You may have wasted some money, or not...
The aux fan will only come on if the AC is operating OR the engine temperature hits a certain breakpoint.
My 300E has a 105 degree sensor.
Try jumping the terminals at the temp sensor. If the fan comes on, the fan itself was not the problem.
Top cause for AC compressor not starting is low refrigerant charge.
Best of luck.
1986 300E 5-Speed 240k mi.