Overheat

Hi,
I recently had an overheat problem in my 1996 Grand Prix, with 3.1 L engine. The radiator tank cracked. Today, I replaced the radiator and noted that the fans were not coming on. The fans and relays tested good. I removed the coolant temp sensor connector and grounded the yellow wire, and both fans came on. So I bought a new sensor. However, the fans still aren't operating. (as a side note, we never noticed this until the air conditioning quit working about 2 weeks back... Fans work fine with the A/C running)
Any suggestions?

Thanks,

M