cat fan clutch

i have a 1996 pete with a 475 h 3406-e engine in it. I notice that when i am at operating temp, and idling the fan clutch kicks in and out constantly, i mean just as soon as it kicks in it kicks out and just as soon as it kicks out in kicks back in. is this normal or is something wrong with the controller? what controls it the ecm or ambient temp or what? does anyone have an idea? thanks

 

i also hear a faint clicking noise under the dash like a relay or breaker clicking in and out, and i can turn the manual toggle switch on and it locks in good, i'm with you probably a bad switch but i was just kind of wondering what controlled the switch so i could know what i was talking about when i went to the shop

 

thanks for the info, all of what you said sounds completely plausible. I'll get it checked out, I assume this truck has had this problem a while because when I bought the truck about 3 months ago the fan clutch was slipping, I had my local mech put a new clutch on it, but i didn't know the thing was kicking in and out like this until I hauled a load with it and got it up to operating temp. I better get this fixed before I burn up the new clutch also