coolant temp variations

I'm guessing the thermostat is the cause of something strange that happens with my car. Occasionally , my temp gauge will climb almost to the red zone , then suddenly drop back to slightly under the half way mark, where it normally stays. It acts like the thermostat opening but happens after I have driven for a few miles and after warm air is coming from the heater. I've never heard of a thermostat closing and reopening while the engine is at normal operating temp. It is not happening often and never goes quite into the red zone , so I guess I can live with it.

Do you have electric fans?

does the air blowing out of the vents get cold? it sounds like your thermostat is sticking. They do open and close to keep the water at the correct temp while the engine is running. I had that happen and I replaced mine, so far so good, knock on wood

For what its worth, after replacing my water pump and clutch fan, my temp bangs around, from 220 to 170, does this with either 195 thermostat I have lying around. Sometimes it settles down at 195 and stays there. Sometimes its bouncy.

With the old cheapo water pump, and half working fan, it stayed at 180, steady, in all weather.
It kinda makes me mad, but I guess now that the car is better, its just worse now.

If you have the automatic climate control, monitor the coolant temperature while driving. Methods are posted here on the Forum. The gauge is reading from a sensor in the cylinder head. In the 94-96 cars the temperature sensor for the PCM is in the water pump. See how the two readings compare and report back.