My miata temp gauge goes hot at high rpm when weather is above 80

I've owned car since 08 n never replaced it fans both workin properly even with a/c on

See this is an old thread but someone else may be looking If your Miata is showing hot and you know for sure it is not over heating then it has to be either the sending unit or the gage itself These two items are connected to each other and nothing else is running to them or is controlled by them The sending unit s mounted on the engine of all cars .As the temp rises the sending unit sends a signal to the gage The gage starts moving up as the coolant in the engine warms. When it reaches a certain temp then the gage stops If the car coolant is not over 180 -200 depending on year and yet the gage says it is hot then the sending unit is most likely bad Most overheating and false signals are simple fixes if taken care of quickly With a Miata do not get pulled into doing a lot of coolant mods they are uncalled for on a stock engine Isolate the problem and fix it