I finally have my 99 ZX2 roadworthy. I have a question about the temperature sensor. I notice that while driving, the dash gauge barely registers above the Cold line, even on 85 degree days. If I sit at a stoplight idling the gauge runs up almost to the middle between cold and hot. Once I start moving again it quickly drops back down near the cold line again. I have never seen a temperature gauge move so much so quickly.

Since I live in Arizona and summer is coming, I want to make sure my dash gauge is working correctly. Could I have a bad temp. sensor? Is there a way to check it?

Thanks all...for any input you give.

 

I know this might sound a little stupid but you might have a thermostat stuck open and the reason why your gauge is moving so much is the air flow going through the radiator. when your stopped at a light there ain't much if any going through it. Make sure that your fan works properly and then change the thermostat.

 

I agree with grindman.
I would go ahead and flush the cooling system if it hasn't been done for a while. Time kills a cooling system because the electrochemical processes don't stop when you turn off the engine.
Also reverse flush the heater core. Some use a few squirts with a power washer to get the crud out of the heater core. Replace or at least test the existing t-stat. I fyou buy a new t-stat get a high quality part.

 

Cooling system has all new fluids, hoses, thermostat, and fan motor. I'm not sure how to reverse flush the heater core. Could it be, or is it likely a faulty/flakey temperature sensor? OBD II scanner doesn't show any codes and when idling and gauge shows almost center with the needle, the scanner says it is running 214 degrees. I put a 180 degree thermostat in it since I live in the heat and thought it would be best to run more on the cool side.

I'll ask the mechanic when I get an estimate on fixing my AC. Thanks for the input.

 

Since you have a completely overhauled cooling system I would not bother reverse flushing the heater core.
I am thinking your cooling system has an air pocket. Do this: