Check coolant levels first.
The fan switch is the one on top of the thermostat housing. The smaller one screwed straight into the head is for the temp guage.
To test the fan- join the two terminals together with a piece of wire, in the plug on the fan switch. Ignition on and the fan should run. If it does then you may need a new switch or it may be that the engine isn't getting hot enough to make it come on. At this time of year the fan won't come on very often.
Tbird
November 2007