Q: Heater blows cool air instead of heat

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Heater does not heat car. Heater blows out cool air only. When heater is first turned on, there is a rattle....after a few seconds the rattle goes away.

My car has 125000 miles.
My car has an automatic transmission.

Hi There, It sounds like you may have a heater core that is not functioning properly. The [heater core]((https://www.yourmechanic.com/services/heater-is-not-working-inspection) is a small radiator like unit that circulates the hot coolant from the engine through the heater core which then uses this warm coolant to heat the inside of the car with the help of the blower motor that blows the warm air through the vents inside the car. The other possibility is that the thermostat may not be allowing the engine to reach a normal operating temperature and since the engine’s warm coolant is the essential source of the heater core supplying heat to the inside of the vehicle, this can impact the warmth of the heat inside the vehicle. The rattling sound may possibly be a blower motor that could be starting to wear out. Occasionally, the bearings in the electric motor will start to make a bit of a rattling sound when they are beginning to fail. I would suggest having an expert from YourMechanic come to your location to diagnose your heating system.

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