Are you sure you're not referring to the 2 auxilliary fans (black) in front of the condensor? These 2 fans are electric and kick in according to A/C and engine coolant temp input. If they run continuously the problem could be an open circuit in your coolant temp sensor or an overcharged/undercharged A/C system.

The single fan (yellowish) attached to the fan clutch is belt driven and will always run with the engine on. It is of the viscous type so the speed varies according to engine heat.

Good Luck

__________________
-Paul-
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi