Fan is coming on early.

[Blue]

My fan used to come on about 3/4 on the gage and shut off about 1/2.  It now comes on about 5/8 and shuts off at about 1/8.  Meaning it is running almost all of the time. 

I think my temperature sensor is bad.  What do you think?

[kris]

Get the ohm meter out and give it a whirl!

[Laitch]

Get the ohm meter out and give it a whirl!

+1
How old is your coolant and where's its level on the reservoir gauge? Is the radiator cap sealing tightly? Is your thermostat working properly?

[Blue]

Decided to replace the coolant yesterday.  The radiator and overflow are full and the cap is tight.  The thermostat is opening and closing.  Still have the fan cycling on sooner than in the past.  I think it is going to wear out the fan because once the needle gets past the blue the fan comes on.

[Laitch]

Decided to replace the coolant yesterday.  The radiator and overflow are full and the cap is tight.  The thermostat is opening and closing.  Still have the fan cycling on sooner than in the past.  I think it is going to wear out the fan because once the needle gets past the blue the fan comes on.

If the thermostat is opening at the correct temperature then it's time to remove the temperature sensor and check its function in heated water as both you and Kris mentioned.

[The Mighty Gryphon]

I would not be as concerned about wearing out the fan as I would the engine never getting to full operating temperature because the fan is cooling things too much. 

Check that temperature sensor behind the radiator.