1994 Dodge Shadow

Heater problem
1994 Dodge Shadow 6 cyl Front Wheel Drive Automatic 178, 00 miles

I have a temp. Guage on a 3.0 V-6 that goes from almost half way to cold when driving, it goes back and forth. I have noticed the fan running also when the guage is no where near the 3/4 mark ( I believe it is supposed to cycle on at 212 degrees). The heater also blows warm air as the guage reads close to 1/2 way but then cool as the guage falls to cold.
This happens all the time. Could this be a thermostat opening and closing or a fan that is running when it isn't supposed to. I already changed the coolant sensor that controls the fan.
Any thoughts would be appreciated.
December 13, 2007.

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