hey guys. this is my first time posting here. seems like a great forum. I have a 03 ford explorer(2wd) and the defrost does not work any more but the other settings for the different vents work. is the switch going bad or do i have other problems any help would be appreciated. thanks
Everyone have a safe and happy new year!!!!!

 

the temp control in the truck is electric. the location the air comes out is vacuum cylinder operated doors. if you looks vacuum or a hose breaks, the cylinders automatically stroke to the defrost location. yours seems to be the odd ball that it will not go to defrost. i would think the cylinder that strokes the damper door is "stuck" since it should stroke to the defrost everytime you shut the motor off and vacum is lost.
the selector sends vacuum to different doors to get the air to that location, floor, vents, outside, etc. so it appears you do have vacuum and controller works. if the cylinder is not stuck, then the control (leaking inside) is always sending vacuum to the defrost door and keeping it closed

 

here is a portion of the manual describing what happens with the 3-4 small vacuum doors. sorry, no photos.

FLOOR
When FLOOR is selected:

--The air inlet duct door is in the no vacuum position, blocking recirculated air and admitting outside air.
--The floor/panel door is in the full vacuum position, directing all airflow to the heater outlet floor duct.
--The temperature can be adjusted to mix airflowing through and around the heater core to achieve the desired temperature level.
--The panel/defrost door is in the no vacuum position, blocking air circulation to the instrument panel A/C registers.
--The A/C compressor will be disabled when FLOOR is selected.
--The blower motor is on.

FLOOR/DEFROST
When FLOOR/DEFROST is selected:

--The air inlet duct door is in the no vacuum position blocking recirculated air and admitting outside air.
--The panel/defrost door is in the no vacuum position directing airflow to the windshield defroster hose nozzle.
--The floor/panel door is in the partial vacuum position, allowing airflow to both the windshield defroster hose nozzle and the heater outlet floor duct. There is also some airflow to the A/C side window demisters.
--The A/C compressor will be enabled when FLOOR/DEFROST is selected to dehumidify the air and reduce windshield fogging.
--The blower motor is on.

DEFROST
When DEFROST is selected:

--The air inlet door is in the no vacuum position, admitting outside air.
--Both the panel/defrost door and the floor/panel door are in the no vacuum position so that most of the incoming air is directed to the windshield defroster hose nozzle. There is also airflow to the A/C side window demisters.
--The temperature setting will determine the amount of air that is directed through the heater core and the amount that bypasses the heater core.
--The A/C compressor will be enabled when DEFROST is selected to dehumidify the air and reduce windshield fogging.
--The blower motor is on.

 

here is another thread. im not sure about this solenoid and how it effected the flow, but something to look into?????

https://www.ford-trucks.com/forums/5...t-working.html