I have not seen this topic posted before. 2008 550 with 65,000 miles. At first the air conditioner was not working at idle and then I had a idrive message that said the car was "to warm" please drive moderately to cool the engine. The fan was not engaging when the car shut off when hot. Hopefully i will get it back today. Bummer!

 

Temp sensor or the fan itself may be bad.
Disconnect the electric fan's power connector and connect 12V directly to the fan and see if it powers up. If it doesn't turn on, you may have to buy a new fan.

 

I had to buy a new fan. expensive

 

How much did it cost to replace the fan? Do you have a CPO warranty?

 

No cpo, out of warranty. $1000, $800 for the part which was in germany. Free loaner for five days while waiting for the part though. They said the car did not over heat but they could not give me a high temperature reading.