ac blows out the defroster ducts

[bean]

my ac started blowing out the defroster and I can't change it. is the switch itself bad or what?

 

[Rearanger]

The blend doors are run off the selection switch with vacuum. The vacuum comes from a vacuum canister or reservoir supplied by the engine. If no postion of the switch works it sounds like you have a leak in the reservoir tank or the lines to it. You'll need a vacuum gauge to test the system.

 

[Spowerback]

I think your system is defective .

 

[pcollins]

I think your system is defective and needs to be recharged or repaired

how charged the A/C is has nothing to do with where it comes out. and obviously its defective. the mechanism that moves the blend doors isn't working, and like said above is most likely the vacuum chamber for it.

 

[bean]

where

where under the hood would i like for this? sounds like it might be a relatively easy fix.

 

[jasongind]

I think your system is defective and needs to be recharged or repaired

 

[Rearanger]

You and I have the same year. Mine looks to be on the passenger side just behind the rad below the upper rad hose and coolant reservoir. Round ball with two thin vacuum lines to it. I'd disconnect the line to the selector switch and attach a vacuum gauge to produce vacuum and see if the blend doors work. If they do then the leak's at the ball or in the line from the engine. Has the engine been operating OK lately? If that doesn't give you blend door operation then you'll have to trace further back toward the dash. You may even have to remove the switch in the dash.

 

[bean]

the engine is running fine. I checked the vacuum lines for any noticeable leaks and nothing. is there a way to test the thing that switches where the air blows? thanks to all

 

[Rearanger]

the engine is running fine.

Then that means you have a small leak that does not affect engine idling etc.

I checked the vacuum lines for any noticeable leaks and nothing. is there a way to test the thing that switches where the air blows? thanks to all

How did you check? Did you use a vac gauge that you could pull vacuum on the line to the switch and hold then see if the gauge drops? To check each of the lines at the switch you'll need to pull the switch, it has one vacuum line in from the reservoir and the other lines go to separate blend door dash pots. Since none of the blend door options are working I still suspect the main vacuum line, unless there is a leak at the switch where the inlet line is.

 

[bean]

help

clueless as to how to do the vacuum test. can someone explain it step by step? thanks.

 

[Big Jim M]

Might sound a little funky...but! Find the vac hose that goes into the firewall. That is the hose that must have vac to operate the doors that direct the air thru the heater and a/c and defroster.. Ok If you don't have a clue do this.
find the end of the hose and take it off of it's fitting SUCK on the this hose! If you get air thru it there is an open hose under the dash...so your problem is under there..
HOWEVER if the hose is tight and you cannot suck air thru it, the bad part is under the hood. The most common leak is at the cannister.. But it could be the hose leading to the cannister also. You can also start the engine and hold your finger over that hose. There should be vac from the canister to the firewall..
There are more sophisticated methods of finding vac leaks but if you don't have the equipment this will work also.
Big JIm

 

[JP02XLT]

My blend door did that once & would not switch as yours is, I took the Vacuum hoses off & made sure they were clear & then used a hand brake bleeder to activate the door a couple times manually & it has worked great ever since.

JP02XLT

 

[modelageek]

My blend door did that once & would not switch as yours is, I took the Vacuum hoses off & made sure they were clear & then used a hand brake bleeder to activate the door a couple times manually & it has worked great ever since.

JP02XLT

Interesting

 

[bean]

?

when you first start the truck it will blow out the vents. but, once the truck runs for a while it starts blowing out the defroster ducts. What's the fix?

 

[modelageek]

when you first start the truck it will blow out the vents. but, once the truck runs for a while it starts blowing out the defroster ducts. What's the fix?

i think the defrost is the default position! Why would it go to the default position?...... is there a vacuum leak somewhere?