Temperature needle on dash dropped to cold as if car was turned off....what's the problem??

[G-639572]

I replaced thermostat and temperature sensor on my 2010 genesis 4.6 probably going on 2 years ago now due to this exact same incident and last night I started the car and watched my needle Starr to climb, but then drop quickly to cold as if I had turned engine off although I had not! I know that the engine was already warm and that it dropping like that wasn't right. Any help would be greatly appreciated!!

 

[NSXNEXT]

Try the simple things.
With the engine cold, remove the radiator cap and let the car warm. Might be air in the cooling system. Once the car warms put cap back and see if that solves the issue.

 

[EdP]

I replaced thermostat and temperature sensor on my 2010 genesis 4.6 probably going on 2 years ago now due to this exact same incident and last night I started the car and watched my needle Starr to climb, but then drop quickly to cold as if I had turned engine off although I had not! I know that the engine was already warm and that it dropping like that wasn't right. Any help would be greatly appreciated!!

Did it come back up? How cold is it where you are?

You start the engine and as it runs, the water heats up and the needle comes up. Once it gets to the temperature rating of the thermostat, the stat opens. The cold water in the radiator rushes in and the sensor drops the needle.

You don't notice this in Key West Florida, but in North Dakota in January you may see it.