Sensor

[narfire]

If you have a warm/hot lower rad hose and when you take the cap off the coolant is flowing, check the fan works. Directly connect 12V to it....works? Yes, perhaps the temp sensor at the bottom of the fan. Are the connections clean and corrosion free? Grounds are clean and corrosion free?

[rlux4]

If the fan works (do as Narfire says, hotwire it to see if it runs) then the problem is in the temp sensor. When the engine is up at 190-195° unplug the connector at the sensor and see if you have continuity between the two wires coming from the sensor.
To hotwire the fan: follow the two wires coming off the fan to the connector, disconnect it and run 12V and a ground to the fan side terminals. You could get the 12V at the starter, but it would be safer to use the "+" side of the coil with the key on. Less chance for sparks. The black wire is ground, blue with black is 12V. The easiest way to do this is with a couple of alligator clips for the 12V and ground, and a male and female bullet type terminal two lengths of wire.
Keep in mind there are two connectors there: the one just upline from the sensor (ground only) and the other near the top of your radiator (power and ground).
Ron

[124JOE]

these cars are known for bad grounds
theres a couple of ground tabs up by the hood hinges
check all of them and use some bulb grease on them

[4uall]

Drivers side ground pod by itzebtze, on Flickr


Passenger side ground pod by itzebtze, on Flickr