Nissan Repair: 95 maxima heater, temp gauge, water temp

Question
the heat in my 95 maxima doesn't blow hot. additionally, when the car is moving, the temp gauge drops to nothing and it comes back up somewhat after sitting still for a bit. I know there's a water temp sensor on it but how do I know if it's the thermostat or the sensor?

Answer
Lou,

The giveaway here is the heater not working and the temperature coming up after the car is stopped.  I would replace the thermostat with a factory Nissan unit.  It costs about $35 bucks at the dealer but it is worth it due to the quality of the unit.  Aftermarket thermostats are not worth it...