* A faulty thermostat. The thermostat regulates the flow of coolant to the engine. If the thermostat is stuck open, too much coolant will flow through the engine, causing it to run cooler than normal. When the thermostat sticks closed, not enough coolant will flow through the engine, causing it to overheat. Either condition can cause the temperature gauge to read high or low.
* A problem with the cooling system. There are a number of components in the cooling system that can malfunction, causing the temperature gauge to fluctuate. These components include the water pump, the radiator, and the hoses. If any of these components are not working properly, it can cause the engine to overheat or run cooler than normal.
* A problem with the electrical system. The electrical system is responsible for powering the temperature gauge. If there is a problem with the electrical system, it can cause the temperature gauge to read incorrectly.
If you see the temperature gauge in your car rising and falling when you don't have the heat on, it's important to get it checked out by a qualified mechanic as soon as possible. This could be a sign of a serious problem with your car's cooling system.
