on the dash below the windshield.
the defrost vent should just pop out by taking a screw driver underneath the sides of the vent cover and prying it up.
The center vent, or defrost duct.
my 1998 gmc jimmy has no floor heat but i have defrost and ven heat
The fastest way to defrost a windshield is to turn the defrost vent on without heat or simply open the windows. Another option is to warm the inside of the car by turning the heater on.
The vent door actuator is operated from the engine vacuum. If the vent control doesn't respond to your demand check the vacuum supply line from the engine, it may be damaged or disconnected. Do this before you tear apart the dash and HVAC box.
When there is a problem with the vent system it dfaults to the defrost setting. Sounds like you have a problem in the doors that direct the air flow.
The most common thing will be that you have a leaking heater core...........
Check for a vacuum leak either under the hood or under the dashCheck the vacuum actuators under the dashCheck the selector control Defrost is the default for this system
The AC on a 1998 Dodge Ram 1998 will only be blowing out the defrost vent if the air handler is not set properly. This can result from a piece of debris getting stuck or a faulty flap.
the ducts can not be hooked up for the vents to work
It is on the drivers side dash just as you open door its by the window defrost vent:)
You have a leak in the vacuum supply to the ac control.