How to fix Windstar heater air control that is stuck in defrost?

Answer 1

I just finished looking at this problem on my 1998 Windstar. The air ducts are vacuum operated. The short answer is that by sealing off the lines that run to the rightmost switch on the heater control panel (the one that controls heating and cooling in the rear of the van), it cleared up the "stuck in defrost" problem. To test the solution, I unplugged the two-line vacuum connector at the back of the switch and put a piece of electrical tape on the connector to seal it. The long answer follows below:

The rest of these answers are correct that a vacuum leak can cause this problem. I have not looked upstream of the switches (into the engine compartment) for any leaks there, but my jury-rig at the rear fan control switch worked. There are two vacuum diaphragms that control where the air flow goes (defrost/vent/floor). These are located by your gas pedal and the center console, and are silver colored metal canisters about one half the size of a soup can. I sucked on these with a vacuum hose and they re-directed the air fine and held vacuum fine, so they were not the problem.

Moving upstream from the vacuum diaphragms there are 6 vacuum lines in the back of the main heater control switch. One of these lines is black, and is a vacuum source (ultimately from the engine). This black line has a tee in it right behind the switch, and another black vacuum line runs from that tee to the rightmost switch on the console (which controls heating and cooling in the back of the van). That switch has just two vacuum lines to it. The black source line, and the white outlet line. I removed that two-line vacuum connector from the rear of the switch, put a piece of electrical tape over the holes, and now the main heat selector switch directs the air properly to the defrost, vent, or floor. That rightmost switch may be bad since I could hear a vacuum leak in it, and moving the switch to different positions or pressing on it could stop the hissing. It is also possible that the connector leaks, but since moving the switch changes or stops the hissing, it is most likely the switch itself. The only other possibility is that if there is low vacuum to the switch in the first place, it could cause the switch to leak. I will check that further.

Answer

There is a vacuum switch that controls an air gate that diverts the air flow to the proper outlet. Blowing air out the defroster is the default setting of the switch. Most common causes of this problem are vacuum leaks. Check the vacuum hose on the passenger side engine compartment first. It usually leaks going through the fire wall. Regardless this problem is most often always the result of a leak somewhere in the vacuum system not the failure of the switch itself.

Answer

I would say that something is binding or broken with the blender box unit. It is the mechanism that allows mixing of the different air settings and is located behind the dash area or under the passenger side area. Hope this helps.

Answer

On my '98 Windstar, this behavior was the result of a vacuum leak; the HVAC modes are vacuum-actuated.

Answer

change the a/c - heat selector switch.

More likely than not you have a vac leak there are to vac lines that run out of the firewall behind the glove box one is red and the other is black trace them out and you will find the leak probably real close to the nipple on the manifold.

Answer

Check for a vacuum leak either under hood or under dash

Check vacuum actuators

Defrost is the default setting for this system

Answer

The most likely is the vacuum line used to operate the swinging doors to redirect airflow is broken or not in place.

You have a broken or disconnected vacuum line that feeds the HVAC (heating, ventilation and air conditioning) system, probably under the hood. When ever there is a loss of vacuum, the system reverts to the defrost mode being the most important mode.

Answer

Your problem can be caused by either a defective heater control switch or more likely a vacuum leak. The leak can be in the vacuum supply tube to the heater control switch or at the engine where the supply tube originates or the vacuum reserve (usually a plastic ball in the engine compartment with two small vacuum lines attached).