1995 1 Ton Diesel Duelly Heat Problem

[Rhummer]

Have a problem with the heat in my truck. When I put the defrost on it seems to draw in too much outside cold air and doesn't blow hot enough. Heater core gets super hot, inside recirc works and truck heats up. What acutates when the defrost is selected turning off the inside recir button?

 

thanks for the help

[Draenor]

You either have a actuator motor is defective. or the blend door is warped or got stuck.

[Rhummer]

How and where do I access the blend door?

 

thanks