[pmcmtnbkr]

first thing i would check is the cooling fans manually spin them feel for any binding listen for any grinding noise. if they dont spin freely and noise free there is a problem. Next unplug the power connectors and apply 12 volts to the fan motor to see if it spins up to speed again look and listen. If these check out its time to look at the wiring to see if there is a fault there. I cant speak for how bmw wires these, most cars use a signal from a temp sensor to a relay to handle the work load of switching power on to the fan. It shouldnt take you more than a few minutes to run these checks. a quick tstat check is once the car has warmed up say around the 200 deg mark the upper and lower coolant hoses should both be hot to the touch or use an IR temp thermometer to check if you cant safely get to the houses.