Question

2000 Nissan Altima, temperature gauge is bouncing, what is the problem?

Answer 1

what code do you have? It might be loose connection and/or bad sensor. If you have not replaced the sensor replace it and double check the wires. There are two coolant temp sensors one feeds the gauge and one feeds the ecu. The coolant temp sensor for the ecu located on back of the engine and the temp sender for the gauge is up front.