Q: Heater only works sometimes

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Ok so here's the deal I let my car run and warm up until my thermostats says it's warm I turn the fan on I get cold air but when I put the air to the from vents I get warmish air. Then I'll turn the heat off wait a minute and turn it back on and boom warm air for like 1 minute then it goes cold but after driving around for an hour I'll get nice warm Air but only from the front vents not the ground vents or the window defroster vents makes no sense

My car has 280000 miles.
My car has an automatic transmission.

The lack of heat being generated by your system may indicate a clogged heater core. 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. I would suggest having an expert from YourMechanic come to your location to diagnose your heating system.

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