Where is the radiator fan temperature switch on a peugeot 406 p reg 2.1 diesel?

I had similar problem locating. I found it on my 1996 LX DT 406. Follow the main water hose from the top of the radiator until it meets the engine. There are two sensors just upstraem of the maniold and one dowmstream on my model. I just disconnected each one until the fans kicked in. It was the RH one upstream of the manifold on mine - but it may be different on a 2.1.

Note that these sensors are not switches but thermistors that feedback actual temperature to the central computer.