my 04 honda civic hester blows cool air
When Hesters (heaters) blow cold air it could be the hose going to the heater core is blocked or the valve is not opening. In reality there are a few other issues that could do this but the easiest to check is flow from the coolant to the heater ,,, other issues could be be ,,,, a malfunctioning ; blender door,, a bad temperature setting sw. ... a disconnected vacuum hose.
There may be something wrong with your heater core.
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