Fans will turn on at eng temp of 212F low speed and 226F high speed.
You are correct, the fans automatically turn on when you disconnect the temp sensor. This is called 'fail safe mode'. Its designed to do that.
The system will only turn the fans on if the above temps are met, OR, if your A/C is on, it see'* a certain pressure at your HIGH side pressure sensor. Because you have no freon/pressure in your a/c system, its not going to turn on and build pressure like its suppose to. No A/C, no fans.
So far, your system looks like its operating normally.
1997 Pontiac Bonneville SEi-SCRAPYARD
2000 Chevrolet Blazer LT 4X4 4.3L
2002 Chevrolet *-10 LS Ext Cab 4X4 5.7 V8