First feel the heater core lines directly at the firewall, if they are both hot but no hot air coming out chances are you have a bad blend door under dash.
If one is hot and the other is cold you probably have a restricted heater core and you should change it or flush it.
If neither are hot it could be a bad thermostat or heater control valve.
Tuesday, December 1st, 2020 AT 9:53 AM
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