• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

ac blows out the defroster ducts


bean

New Member
Joined
Jan 27, 2009
Messages
22
Reaction score
0
Points
0
Location
Temple, Texas
Vehicle Year
2003
Make / Model
Ford
Engine Size
3.0l
Transmission
Automatic
my ac started blowing out the defroster and I can't change it. is the switch itself bad or what?
 


Rearanger

Active Member
Joined
Feb 4, 2008
Messages
1,429
Reaction score
23
Points
38
Location
Southeast USA
Vehicle Year
2003
Make / Model
Ford
Transmission
Manual
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

Banned
--- Banned ---
Joined
Feb 16, 2010
Messages
429
Reaction score
0
Points
0
Location
California
Vehicle Year
2010
Make / Model
FORD
Engine Size
v6 4.0L /
Transmission
Automatic
I think your system is defective .
 
Last edited:

pcollins

New Member
Joined
Mar 19, 2010
Messages
957
Reaction score
7
Points
0
Location
Middle of Nowhere, NY
Vehicle Year
2012
Make / Model
GMC
Engine Size
4.8L
Transmission
Automatic
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

New Member
Joined
Jan 27, 2009
Messages
22
Reaction score
0
Points
0
Location
Temple, Texas
Vehicle Year
2003
Make / Model
Ford
Engine Size
3.0l
Transmission
Automatic
where

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

Rearanger

Active Member
Joined
Feb 4, 2008
Messages
1,429
Reaction score
23
Points
38
Location
Southeast USA
Vehicle Year
2003
Make / Model
Ford
Transmission
Manual
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

New Member
Joined
Jan 27, 2009
Messages
22
Reaction score
0
Points
0
Location
Temple, Texas
Vehicle Year
2003
Make / Model
Ford
Engine Size
3.0l
Transmission
Automatic
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

Active Member
Joined
Feb 4, 2008
Messages
1,429
Reaction score
23
Points
38
Location
Southeast USA
Vehicle Year
2003
Make / Model
Ford
Transmission
Manual
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

New Member
Joined
Jan 27, 2009
Messages
22
Reaction score
0
Points
0
Location
Temple, Texas
Vehicle Year
2003
Make / Model
Ford
Engine Size
3.0l
Transmission
Automatic
help

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

Big Jim M

New Member
Joined
Apr 18, 2008
Messages
2,728
Reaction score
30
Points
0
Age
86
Location
Austin
Vehicle Year
2002
Make / Model
Ford
Engine Size
4.0
Transmission
Manual
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

Member
Joined
Nov 23, 2008
Messages
466
Reaction score
8
Points
18
Location
Indiana
Vehicle Year
02
Make / Model
Ranger
Engine Size
3.0
Transmission
Automatic
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

Active Member
Joined
Jan 31, 2009
Messages
2,241
Reaction score
14
Points
38
Location
Boston, MA
Vehicle Year
2004
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Automatic
2WD / 4WD
4WD
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 :icon_idea:
 

bean

New Member
Joined
Jan 27, 2009
Messages
22
Reaction score
0
Points
0
Location
Temple, Texas
Vehicle Year
2003
Make / Model
Ford
Engine Size
3.0l
Transmission
Automatic
?

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

Active Member
Joined
Jan 31, 2009
Messages
2,241
Reaction score
14
Points
38
Location
Boston, MA
Vehicle Year
2004
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Automatic
2WD / 4WD
4WD
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?
 

Sponsored Ad


Sponsored Ad

Staff online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Truck of The Month


Kirby N.
March Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top