Mercedes: Aux Fans problem, double fans, compressor clutch

Question
I have a 1995 M-B SL320 with 120000 miles.  The two auxiliary cooling fans, in front of the radiator, will not operate when activating the A/C.  The fuses are fine, the blades turn freely by hand and make no unusual noises.  Do you know the problem and can tell me how to diagnose and fix?

Answer
Hello Dave,
You need to verify that the fan motors are working. One fan is controlled by a coolant thermostat, and cycles as needed to help keep the radiator cooled and I believe that both fans are operated through the AC control system. Double fans are needed to provide the additional air flow during AC condens3r use.

If you can locate the fan wiring connection plugs,(usually near the fan frame, you can rig a set of wires to tap the fan directly to the batter terminals. This will tell you that the motors are able to turn if power is applied. YOu will just need to set one wire to the negative post and just momentarily tap the opposite terminal to see of the blades rotate.
Do you know if you A/C compressor clutch is actually engaging when you trunk on the Climate control?
Also, If yo have an economy light there may be a fault with that system because it controls the AC compressor, and possibly the fans as well.
The fuel economy system turns off the pump when the engine is under a load as going up hills. The five additional HP that on average is required to operate the AC system is better used to move the vehicle.
Good Luck Let me know what you find out.
Rob