I've had this issue for as long as I've owned the car and thought that when I had the timing belt and thermostat replaced this summer the issue would go away, but apparently I was wrong. I've also replaced the coolant sensor which was a green with a new green one and the quirkiness still is there. The motor always seems to run cold no matter how long the motor is run. With the AC on the motor is cold in the summer and in the winter when I turn the heat on it produces very hot air and actually drops the engine temp down...Usually it gets up to the first mark no problem and then fluctuates between cold and the second mark but it will only reach straight up if it sits for 10 or so minutes after being run for about 30mins but as soon as I start the car back up it drops back to cold and the fluctuating cycle beings once again

It all seems so strange to me so I logged it some on a 3hr long drive and thought you all might have some insight? Heres the log and a picture after 2hrs of driving

https://docs.google.com/leaf?id=0Bym...ut=list&num=50

 

No ideas?

 

sounds like a bad thermostat. even though it was replaced, the new one could've been bad. it's pretty common