I just went through the same headache.

1. check to make sure you have coolant in yr radiator first - if low then u have a leak so look at all possible areas for leaks, hoses, drain plug, bleed plug, and gaskets. Do you smell anitfreeze? you should see dried A/F somewhere if you have a leak. If your level of A/F is low the fan switch will not know your car is in need of the fans. Also try seeing if you can start the with with your AC on. If the work then your fans are fine and it could be the switch (~$50)

If no leak then do the 2 test I attached for you.