idle Overheat and fan?

My fan does not run while the engine is running casueing it to overheat while idleing for more then 5 minuts at a time. If im moving at least 10 mph im fine. When I SHUT down the engine THEN the fan goes on? whats going on here?
Please help!?

thanx
Mike

sounds like it could be your thermostat, have you checked that, when was the last time it was replaced? my teg used to over heat at idle and cool down while it was running…i changed out the thermostat and now it runs at the correct temp

HTH
Jeff

Were is the thermostat located. How can I check to see if it is working correctly?

-Mike