I was driving around last night and saw that my water temp read 210. I was like, that's kinda warm so i switched on my fan. Just a couple seconds later i looked down and it was at 180. I thought to myself, there is no way it cooled down that fast. so as i kept an eye on it, the damn needle would move from 180-230 randomly. WTF??? I changed the sending unit less than 3 months ago when i did my opti. The only thing is i used a ****ty AutoZone part. Do you think this could be the culprit? What is going on here. Any help greatly appreciated.

 

There are 2 water temperature sending units. If you replaced the sending unit by the opti that is the one that tells the pcm the water temp, the other sending unit/sensor is in the head or block on the driver side and it tells the gauge in the car what the temp is. I would try to bleed the system, and maybe get a scanner to see what the pcm reads. Maybe you have a faulty sensor?