http://www.w-body.com/forum/viewtopic.php?t=15018
Sorry for the crosspost, but I needs me some help.
The sensor on the radiator is the "coolant level" feed. The one under the thermostat is for the water temp..feeds the gauge, and the other one at the rear of the block near the firewall is block temp.
Yeah, I was pretty sure the on IN the rad. was the level, but not for positive.
You have two fan relays in the fuseblock above the left front tire (passenger side). One is for primary cooling fan, and the other for the secondary. There also may be a fuse there (not sure). Make sure both of these relays are working and if there is a fuse present... make sure its not blown.
-jheiv
EDIT: Check the w-body board.