Can't identify something on an ML500 - PeachParts Mercedes-Benz Forum

stephenson · #1 01-13-2003, 07:50 PM

Neighbor just bought a ML500 ... while examining the engine, I noticed what appears to be an electronic device inside an aluminum assembly that is mounted on the edge of the cooling fan housing .... the aluminum body has several heat sinks cast into it and the assembly hangs out about 2 inches into the airstream just downwind of the fan blades ... wire bundle with larger red wire runs from device down to left of the block (facing the rear) ... I'll bet someone knows what this is.

I guessed an electronic receiver, but that doesn't require that much power. Generating device for the spark plugs?

myarmar · #2 01-13-2003, 09:36 PM

This is probably electric engine fan with built in PWM regulator. It replaces engine driven fan and viscous clutch. It has 550 Watt motor and 100 Amp fuse for circuit protection. I was sure its only used for diesels?

stephenson · #3 01-13-2003, 09:44 PM

I probably wasn't clear ... the device looks electronic with heat sinks ... something obviously that puts out a lot of heat (ref the sinks and also that it sticks into the cooling airstream that is put out by the fan itself.

It is not inside the fan shroud, but rather bolted behind it (it is about 4" by 8" and looks like it was simply bolted on the fan shroud ... I assume it was to keep it cool).

myarmar · #4 01-13-2003, 09:56 PM

No, I was not clear: I think its PWM regulator for the fan.
Mike

stephenson · #5 01-13-2003, 10:10 PM

Oh ... I get it. Makes sense then ... so, it regulates fan on/off circuit with sensors on engine and provides power to the motor?

myarmar · #6 01-13-2003, 10:27 PM

Not only on/off. It regulates fan speed by changing pulse width of 12 VDC power to the motor depending on the engine coolant temperature and/or AC refrigerant pressure.

stephenson · #7 01-14-2003, 08:14 AM

So, unlike binary approach with former electric systems (system circuit meets set temp and then turns on and then meets certain temp and turns off) this actually puts fan speed into a single sensing and response loop?