Radio/tape Cd Player problems of the 2007 Toyota Tacoma

When heat control dial is turned from cold to hot, an inside door within the heating/cooling system closes off. This keeps any hot air from blowing into the cab and through the defroster. This decreased air volume from hvac vents will not heat the cab in cold weather and will not properly defrost the windshield in wintry conditions as no hot air will blow. Toyota service bulletin (t-sb-0072-09) covers this costly repair. The inability of the defroster to provide hot air to the windshield has caused me to pull over several times due to inability to see through it either from internal condensation or from ice buildup during times of precipitation and freezing conditions. Further, with the heater not able to provide hot air into the cab, occupant safety is at risk in times of extreme weather during both driving and/or times the vehicle might become stranded. This condition occurs in all modes of operation, both driving or idling in park. Air velocity tapers off as the heat control is increased (to the right) to the higher settings effectively cutting off hot air flow into the cab. This is both when the vents are open and when in recirculation mode. See attached file for reference. Primary safety concern is visibility through the windshield during inclimate weather and occupant safety in colder conditions. This is not a new problem with my vehicle- but has recently become a very significant safety concern due to recent weather conditions and temperatures. I cannot load the pdf file (t-sb-0072-09) as it is too large.