Serena Van Cooling Fans

Hi all
I have a UK Spec Serena Diesel van and the cooling fans on the radiator are running all the time the ignition is on I have a manual which shows the Radiator having a Thermo switch to control the fans but the position on the rad is blanked off and has never had a switch, but according to the last owner the fans used to switch on and off dependent on engine temp, any ideas
Thanks

The coolant temp switch may be located in the thermostat housing..... it's a screw in sensor normally.