dash air blowing out of defrost vents?

[softballdad25]

One more thing.....when the selector knob is on A/C or Max A/C....I still have some air flow through the front window defrost ducts as well as the dash vents. Is this normal?

[softballdad25]

One more thing.....when the selector knob is on A/C or Max A/C....I still have some air flow through the front window defrost ducts as well as the dash vents. Is this normal?

[Argosy]

No. Defrost is generally the default in case of a failure of the vacuum system, you can still see to drive.

You could have cracked vacuum lines or fittings, kinked lines, weak motor. There are foam seals on the doors inside the plenum, they can come loose and stop the door from closing completely.

[John-D]

Depends on what you mean by "Some Air" If I were designing a car I'd put "Some Air" into the defrost system on AC but not much more than 10%.

As the other reply said, Defrost is the default should the vacuum system fail, but that will be most all the air (100%) And if you have an air dam (Door) that has a bad seal on it, that would allow air to flow past it as well.

If it's only a little bit of air in the defrost system.. I'd not worry about it.

[mountainkowboy]

Default vacume failure

[softballdad25]

Thanks to all responses. It is just a little bit that blows in the defrost vents and we're still getting good air flow out of the dash vents.....we're probaly fine. I will check for vacuum leaks and also check the air dam. It's all good here in the desert!