I changed the thermostat and flushed the heater core, still no heat
My car has 153000 miles.
My car has a manual transmission.
The first thing to check is for both heater hoses going into the heater core to be hot. If one is hot and the other cold or just warm where the other one is hot then you have a blocked heater core. If both hoses are hot then the problem is inside the vehicle on the blend door of the heat control. The blend door has an electronic actuator then may be not moving the door or the door is stuck or broke inside the case. Remove the actuator if it is not moving when checked. Test the door manually to see if it moves freely and controls the temperature for you. Replace actuator and calibrate the actuators.
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