I know that when I bought my E420, the radiator fans were inop. as well. It turned out that there's a power resistor that had a corroded contact (the resistor allows low speed fan operation). I replaced the resistor, took about 2 hours because the damn thing is buried in the engine bay, like everything on a M119 engine, and fans now work fine.

I doubt that your radiator fans will be running in winter - the main fan should do the job fine until things heat up.

Troy
1995 E420