The cooling fan on my 2002 E430 has been running a lot more often than I seem to recall from previous summers.

Can anyone describe the engine fan cooling system logic (i.e. what triggers it to come on, which sensors are involved, etc.) on this 210.083 vehicle?

The symptoms that I have are:
(A) Cooling fan not engaged when starting the car (cold)
(B) Cooling fan engages when the H20 temp reaches ~85C (based on the dash gauge) with the A/C running
(C) Once the cooling fan is engaged, is never seems to disengage (until the engine is shut off) - even at highway speeds 55+ I can still hear the main fan running (the H20 temp gauge on the dash is solid at just over the 80C line)

This seems to have arisen after I replaced the voltage regulator on my alternator in April - so potentially I damaged some of the wiring or inadvertently disconnected some sensor.

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Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE