help with temp lever in AC truck

[gman]

Question........the temp lever, controls a door that appears like you need to access it from the engine compartment. Is this correct? I've got my ductwork apart on the inside of the truck but I can't seem to get to the door for the temperature control from the inside. I've gotten to the outlets door and the defroster door and have those working great now. But when I slide the "bowden" cable (what its called in the service manual) for the temp lever, the arm on the top of the firewall just above the blower motor moves about 2 inches max. When I disconnect the cable at the arm on the firewall, it won't move anymore by hand than it does with the cable. I'm assuming there may be crap in there or that the arm that attaches to the door may need some attention but I'm not sure how to get to it. I can always feel very warm air coming from the vents and I'm assuming the door isn't closing completely. Anyone know the best or easiest way to access the temp door? Any help would be appreciated. Thanks alot!