> Just wire in a manual switch.  When the temp gets to a certain point, flip
> the switch.

The downside to this is that when the radiator gets really hot, the fan is
supposed to remain on for several minutes after you shut off the van.  If
you are using a manual switch, this will require waiting in the vehicle for
a few minutes when you reach your destination.

- Ron Salmon
 The Bus Depot
 http://www.busdepot.com