I have just purchased a 560 SL...and have never owned one before... and noticed that the fan in front of the radiator (not on engine side of radiator) does not run when the car is idling. When should it be running? does the engine have to reach a certain temperature? Also when replacing the fuel pump relay is there any special tips? Thanks

The fan is activated by a pressure switch on the a/c high side. You should be able to find the switch at the dryer. It turns the fan on at high side pressure on the a/c system. Do a search.

__________________
Jim