cooling fans not coming on?

[Zack]

ok so the drive to vegas was torture on the msp. The couple stops we took(barstow baker and primm) I checked the coolant and it was literally boiling over in the overflow tank. the needle never past the halfway point. I started to wonder if my fans were even kicking on. heres the test I did

car off ac/heater off no fans
car in on ac or heater on fans kicked on.
car in on with ac or heater off no fans(this shocked me because with it boiling over id think it was hot enough for the fans to go on

even car running with boiling coolant at idle no fans, not until I turned the AC or heater on

any ideas?

 

[Wagonbacker9]

fan relay may have gone bad. cheap part, I'd at least start there.