Got a little issue with my 2002 AVK 3.0 avant

aux water pump's working on output test, but will not work after the car is off, causing the engine to get too hot when parked after a drive.

Need to know where the temp switch is for this function. The ECT is new. I was expecting another switch in the cooling system somewhere (like the bottom of the lower hose), but there isn't one on the AVK... 3.0

Thanks in advance for any help,
Mike