fans don't come on when temp is high.

@henry2 possibly your fan relay or the coolant temperature switch. Disconnect the coolant temp switch located on the bottom of the radiator and see if fans come on. When the switch is disconnected, the fans should run all the time when the engine is running. If that still does not work then you will have to suspect the sensor for the computer. It is a bit cumbersome to test it by placing it in hot boiling water and testing it with an ohmmeter to see if it closes the contact at the right temp. I just replace mine ;-) After that check the relay to see if it works.