cooling fans

When I start the truck both fans come on ( truck is cold and ac is NOT on). Then the fans go into hi after about 30 seconds. The relays are all good, the temp gauge at instrument panel seems to read accurately. When I turn the truck off the fans go off. Any ideas???

went out and battery is dead. hooked up jumper cables and cooling fans come on as soon as i connect clamps. been sitting for 24 hrs. drive about 26 miles notice with a/c on idles rough and almost dies.(runs great with a/c off). next day battery dead again. new battery. as soon as i hookup...