A/C Vent Contro;
billstewart
05-13-2007, 02:17 PM
Suddenly my Windstar has started to, on its own, cycle through the vent controls. When I start-up the A/C in Max Air or Normal Air the air first blows through the windshield setting, then the floor setting then after several minutes to the setting I selected - usually the dual setting. Also, now instead of the auto locks setting as I put the car in Drive and pull forward a few feet, it takes about a minute of driving before they set themselves. What's with this? Is it a computer problem?
wiswind
05-13-2007, 05:35 PM
The AIR controls are vaccum controlled.
The default position.....which is where they will be if you loose all vaccum to the system....is the defrost (all air to the windshield) position.
There are several vaccum controlled actuators that move doors to direct the air to the selected position.
My guess is that there is a problem with the vaccum supply to the system.
Less likely would be the selector switch....although that failure seems to be more common with the auxillary (rear) control switch.....the one for the main (front) seems to hold up better.
Also, the actuators themselves seem to hold up very well.
The vaccum comes from one of the many vaccum lines that connect to the back side of the upper intake manifold on the engine.....then the line goes to a resevoir box that is mounted on the passenger side inner fender....then a line from that goes through the firewall into the passenger compartment.
A cracked, loose or collapsed vaccum line is the most commone issue with these controls.
The control of the temperature is electrical......and a electric motor drives a "blend door" to select how much air passes over the heater core.
This is a completely separate control.
As for the door locks......I don't know....I thought that they worked at a certain speed.....and if that is the case...they would most likely be actuated by the reading from the speed sensor....which is located at the back side....mid point on the transmission.
That is a bugger to change....so hopefully, that is not the problem.
The default position.....which is where they will be if you loose all vaccum to the system....is the defrost (all air to the windshield) position.
There are several vaccum controlled actuators that move doors to direct the air to the selected position.
My guess is that there is a problem with the vaccum supply to the system.
Less likely would be the selector switch....although that failure seems to be more common with the auxillary (rear) control switch.....the one for the main (front) seems to hold up better.
Also, the actuators themselves seem to hold up very well.
The vaccum comes from one of the many vaccum lines that connect to the back side of the upper intake manifold on the engine.....then the line goes to a resevoir box that is mounted on the passenger side inner fender....then a line from that goes through the firewall into the passenger compartment.
A cracked, loose or collapsed vaccum line is the most commone issue with these controls.
The control of the temperature is electrical......and a electric motor drives a "blend door" to select how much air passes over the heater core.
This is a completely separate control.
As for the door locks......I don't know....I thought that they worked at a certain speed.....and if that is the case...they would most likely be actuated by the reading from the speed sensor....which is located at the back side....mid point on the transmission.
That is a bugger to change....so hopefully, that is not the problem.
Automotive Network, Inc., Copyright ©2026