I'm wiring up a switch so I can turn the fan off, have it run low and have it run high. It's partially installed now so I have low and off. After reading about running with the fan off, I wanted to see what would happen if I did that with my V6. After driving on the freeway for about 15min I got off at my exit and stopped at a couple red lights. I turned off the fan and the gauge didn't move. Later I finally got the gauge to move by sitting at my parking spot and reving the engine for about 20sec.

Of course it was only about 70deg out and I didn't idle at the red lights very long, maybe about 1min. So I guess the fan doesn't do too much unless under really hot conditions.