The way the system works is the pcm monitors the temp via the sensor. The sensor has two outputs, one to the gauge and one to the pcm. The pcm grounds a relay to power the fans at low speed, it grounds another relay to power the fans at high speed.
By unplugging, I'm unsure what is being accomplished. The pcm should see no temp and default the fans to on high speed as a safety. Then it appears the pcm sees the temp and turns them off.
I've known our dash gauges lie badly at times. Do you have a way to get a scanner on it to see the temps the pcm see'*?
00 Regal GS: All kinds of cool stuff.