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does it ever go to defrost when in overdrive?
Mode Door = vacuumBlend Air Door = electric actuatorFresh/Recirc door = vacuum
if the heater core hoses are still hot then the blend air door may be bad
both hoses remain hot
Yes you wil want to get the blend door actuator out and check its operation but it is probable bad. 30 percent of the time its connection and wires.
where is blend door located I have checked both vacuum doors
one moment Let do some checking and see if I have a image for you