Unplug the radiator connector, turn on the ignition and short the wire connector contacts together with a piece of wire. If the fan doesn't come on, check the fan wire connector on the radiator top shroud. That's the usual problem followed by the fan blade being mechanically impinged by its shield. If the fan runs in the test but the temp gauge sometimes gets to four bars or more, in stop and go traffic especially, you can take the fan switch out of the radiator at test it for electrical conductivity in boiling water.
If the temp gauge exceeds 3 bars in clear traffic, the problem is not the fan but possibly a clogged radiator, internally with sludge/scale or externally with dirt/bug bodies/mud/etc.. Other possibilities besides a clogged radiator are a stuck thermostat, lack of coolant or a clogged water passage/hose.