Does your car have the viscous fan or the electromagnetic one?
If its the Viscous fan, then it should lock up at around 100c by the viscous in the clutch congeling with the heat of the engine..if its not, then the clutch has had it and a new one is needed,
The electromagnetic fan is operated by a switch on the top/front of the engine block, the water temp activates the switch at 100c approx and the fan is then locked on by an electric clutch. It may be that the switch has gone in this case, as they arent the most robust things in the world. They are too expensive, £14.99 + VAT her in the uk, so i would imagine about $25-$30 or so.