Here's an old thread. I noticed my M4 auxiliary fan doing something very similar to what was described with the replacement N65 pulse controller. That's within the fusebox. N65/1 up front came in MY97, I believe. Note that the 40 amp Maxi-fuse at position 20 is not present on the E300. Gas models only? I don't know which fuse protects the M4 circuit.

Turning the control current to 10 by pressing both AUTO buttons for >10 seconds as described in the diagnostics caused the fan to attemp to start about once every five to six seconds. The N65 would make no noise (it appears to control the fan using MOSFET's rather than relays), but the fan clicked about five to ten times with each start attempt. "Helping" the fan by turning it by hand right before it would attempt to start caused full-power operation to ensue and continue until the control current was turned off (by pressing both AUTO buttons >10 seconds again).

With the engine running and the vehicle stationary, the fan starts when the control current is small, perhaps less than 3. At 2 it definitely starts and runs, and at 4 or above it just clicks.

The M4 in the car is not OEM, but is an aftermarket part marketed on Ebay and uses dual fan motors. Both motors are smaller than the original one motor in the OEM M4. I'm not sure when this behavior started, as I can't see the M4 in operation while driving, but it worked the last time I idled the car while stationary.

So now some questions, and hopefully someone knows a bit more than was addressed above.

Does anyone have a schematic for N65? The part number is above.

What is the normal startup current for M4? How long is it applied by N65, and is it supposed to be pulsed while starting? Mine is getting a number of pulses.