Test the temp sensor it sounds like the sensor is working intermitently
Temperature Gauge Inoperative Or Inaccurate
Disconnect the engine coolant temperature (gauge) sensor (usually a dark green wire).
Insert a 44 ohm resistor between the connector and ground.
Turn the ignition switch to the ON position. Does the gauge now read high, approximately 260 F (127 C)?
If the gauge now reads high, check for a poor connection. If okay, replace the gauge sensor.
If the gauge shows no change, check for a bad connection at the instrument cluster, or a short to voltage between the instrument cluster connector and the gauge sensor. If these circuits are okay, it may be necessary to service the instrument cluster.
Locate the engine coolant temperature gauge sensor. It is usually below the coolant connection, just below the bleeder connection.
Partially drain the cooling system to a level below the sensor.
Unplug the electrical connector.
Unscrew the sensor from the engine.
Thread the sensor into the engine. Use care not to damage the "pigtail" wire.
Reconnect the lead wire.
Refill the cooling system with the proper mix of DEX-COOL and water and properly bleed the cooling system.
Check for leaks.
Saturday, January 31st, 2009 AT 9:06 PM