lets make sure its the blend door and not the heater core in need to be flushed
do a self diagnose test on the system and let me know what you have for codes if any
ENTERING SELF-DIAGNOSTICS
Ensure in-car temperature is 40-90°F (4-32°C) as false in-car temperature sensor DTCs will be displayed. Simultaneously depress OFF and FLOOR buttons, then press AUTO button within 2 seconds. The display will show a dashed line in center of display window for up to 30 seconds while test is running. Record all DTCs as displayed.
Self-diagnostics can be initiated at any time with the resulting DTCs being displayed. Normal system operation is stopped when system is in self-diagnostic mode.
Nov 6, 2009 at 7:06 PM