2004 ML500 overheating

[300EE320]

Hi,

I have 70K miles and have not ever had a problem with overheating. Today, at low speed, the temp is running up to 120, and the A/C is very weak. This started abruptly today, so I know something went wrong, not just a blocked flow to the radiator. Coolant level is correct. This model has only an electric fan, there is no fan clutch. I popped the hood quickly with the temp at almost 120, and the electric fan is barely moving, just free wheeling slowly. It is moving under it's own power, but I'd expect it to be really moving some air.

There is a finned aluminum module at the top of the fan on the passenger side. Is that the fan controller? Can I test this by unplugging the harness and jumping across the two pins on the module? I checked the voltage across the power wires and it is full battery voltage, 12 with the engine off and 13 plus with it running.

Please help me to troubleshoot this.

thanks!
Dennis

[mbdoc]

That picture is of the intergrated fan module & most likely IS the problem.

[300EE320]

Can I bypass the module to isolate that as the problem?

Is that a part I can replace, or is it a part of the auxiliary fan assembly?

That whole assy is expensive, and I'd sure like to verify that it is bad before I spend the money.

Thanks for your help!!

Dennis