m car heater gets warm but not hot.the engine heats up fine.when i stop at a light the heater temp.goes down then goes back up when i start driving gain.does it sound like i need a new thermostat?
My car has 1350000 miles.
My car has an automatic transmission.
It is possible that the thermostat is stuck open. When this happens, the engine can run much cooler than it is intended to. Running "too cool" can effect fuel mileage, emissions, and heater output. Most modern engines operate around or above the boiling point of water - 200-225 degrees. The thermostat generally opens when the coolant reaches 190-195 degrees. Part of it’s job is to restrict coolant flow so the engine can reach those temperatures. If the thermostat is open constantly, the engine may never reach operating temperatures. Have a certified technician inspect and/or replace the thermostat.
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