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Q: My heater only blows cold air

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I just put in antifreeze and a new thermostat and it's still blowing cold air. What else could be wrong?
My car's transmission is unknown to me.

Check the operation of the heater control valve, which is often located on the engine compartment firewall. If that valve doesn’t move to the commanded position, or move fully, you will have a no heat condition. If the valve is operating properly, then either the blend door(s) is non functional, the heater core in the dash area is plugged, the hoses are restricted, or there is trapped air in the system preventing coolant circulation. If you request a no-heat diagnostic, the responding certified mechanic will determine which of the foregoing potential faults is the cause and give you an estimate to repair.

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