- If you need clarification, ask it in the comment box above.
- Better answers use proper spelling and grammar.
- Provide details, support with references or personal experience.
Tell us some more! Your answer needs to include more details to help people.You can't post answers that contain an email address.Please enter a valid email address.The email address entered is already associated to an account.Login to postPlease use English characters only.
Tip: The max point reward for answering a question is 15.
Check all vacuum lines first for any possible leaks especially if you have a flow control near firewall or hoses going through firewall. If you feel hoses going to heater core, are they both hot to touch when engine at normal running temperature? Coolant level is up, and been bled properly? Did you have to add coolant lately for any reason?
The defrost position is the default for safety so that air always blows on the windshield in case of frost. The most common problem is a faulty blend door under the dash. In most cases the door must be calibrated with a scan tool if you replace it.
CHECK all the vent hoses, are they connected, no ob strucctions, when the last time you replaced the cabin air filter ? do you have one? look @ your owners manual, also, you may need to have several heater controls, or other control on as well, see owners manual, anything fall into the defroster vents ? replace thermostat @ engine. see how this works for you, good luck
Common question on this site. On late model cars, the vents are controlled by blend door motors. Small electric motors open and close doors to direct air flow. Chances are you have a blend door that is stuck or a failed motor. The default position is the defrost to make sure the windshield is always clear. Someone will need to look behind the dash to see if all of the doors will move on demand.
Inside the heater box (under the dashboard) there are actuators that are similar to the ones that open your power door locks, they do go bad especially if any water leaks in from a bad heater core or windshield leak.(down the defrost vent grate). Also old age, my truck is a 2000 and I have replaced a couple of actuators.
Car manufacturers use the defrost mode as a default for safety reasons. Being they want you to be able to defrost the windshield no matter what. So when something goes wrong the system automatically goes to the defrost mode. You most likely don't have the vacuum hose connected under the dash at the climate control assy. Or if this vehicle doesn't use the vacuum hose style you may have not plugged in one of the connectors under the dash or behind the climate control assy. Good luck.
You have a vacuum leak. Defrost is the default postion(no Vacuum). Start by finding the small black vacuum line near the heater hoses at the fire wall under the hood.Trace it back, it should go to a square black reservoir . Not totally sure exactly where it is located on this model,shop manual doesn't show a very good pic, but it states to remove wiper arm and pivot shaft to remove it. You will see a second line going from here to intake manifold vacuum port. Make sure you don't have a leak there somewhere.