The place to start is by having your mechanic connect a scanner that will display live sensor data and see exactly what the Engine Computer is seeing for coolant temperature. That uses a different sensor than for the gauge. If the coolant temperature is fine but the gauge is reading high or erratically, the most common suspect is the wire to the sensor is grounding out on a spot that is rubbed bare. The gauge's sending unit could be defective too but those don't really cause a lot of trouble.
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Friday, July 5th, 2013 AT 3:52 PM