1991 Camry fan problems

Hi All.
Hopefully someone may be able to help me here.
My daughters car (91 camery has two fans on the radiator). I believe one is for the A/C and the other for overheating. The problem is that both fans come on as soon as the ignition is switched on.
This happens even first thing in the morning when the car is cold.
I have had both relays replaced (as I was told that they can get a bit sticky and jam) but the problem is still there.
I have also been told that it may be a sensor ????? (what ever that means)
Would anyone else have any idea's what may be causing this.
Thanks all
Cheers
Peter

 

You can find a wiring schematic here:

http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/14/09/20/0900823d80140920.jsp

Scroll down to #25 (it says 24 when you open it).

Could be the coolant sensor, whcih tells the system when to turn the fan(s) on. Having them turn on all the time is not necessarily a bad thing; I have the auxilliary fan on my wrecker wired to run all the time (the main fan is belt-driven).