Climate Control Issue - Only Defroster
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Mountain Pass
Joined: Jan 2012
Posts: 182
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From: Lebanon, OR
Climate Control Issue - Only Defroster
When I bought my '99, I noticed an issue where, if I had the climate control set to AC or MAX AC, it would occasionally shift itself to the defroster (not the switch, of course), and then rock back to the vents.
Now, it stays in the defroster, and won't move anywhere else.
Any thoughts on the issue? Blend door failure, maybe, or would that only be the issue for a heat/cold problem? It blows cold/hot just fine, just not in the position I want it.
Just trying to figure out what I'm going to need to do to repair.
Now, it stays in the defroster, and won't move anywhere else.
Any thoughts on the issue? Blend door failure, maybe, or would that only be the issue for a heat/cold problem? It blows cold/hot just fine, just not in the position I want it.
Just trying to figure out what I'm going to need to do to repair.
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Mountain Pass
Joined: Jan 2012
Posts: 182
Likes: 0
From: Lebanon, OR
Any suggestions on where to start/how to start, or possibly a link to a tutorial specific to our trucks?
I'm typically pretty handy, and do most of my repairs myself, but this is a system I'm completely unfamiliar with.
I'm typically pretty handy, and do most of my repairs myself, but this is a system I'm completely unfamiliar with.
Posting Guru
Joined: Mar 2014
Posts: 1,468
Likes: 5
From: Salt Lake City, utah
Here’s a little light reading
https://www.ford-trucks.com/forums/a...2&d=1443817297
This is for the EATC but I will keep looking for the other PDF
https://www.ford-trucks.com/forums/a...2&d=1443817297
This is for the EATC but I will keep looking for the other PDF
Fleet Mechanic
Joined: Oct 2008
Posts: 1,321
Likes: 250
From: North Texas
Buy a cheap vacuum gauge if you dont have one to see if hubs hold vacuum. If they do trace up to the pump. If lines are good, check solenoid or pump. There are some good videos on YouTube if you need a better picture of the process.
Senior User
Joined: Feb 2010
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If the truck has manual hubs, check to see if the vacuum lines are still there, but, not attached. Typically, when you only have defrost, this is either a vacuum, or blend door actuator problem. It will default to defrost to keep the windshield clear. Kind of a safety feature. Also, I believe if you look under the glove box, you may see a cluster of vacuum lines, going to a plug, make these are connected securely.
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Mountain Pass
Joined: Jan 2012
Posts: 182
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From: Lebanon, OR
Will go dig into both when it stops raining.
I've owned the truck for about 14 months (bought in April of 2017). First summer, little issue (happened a couple times, didn't think much of it). Winter, left it on defrost. When things started warming up 2-3 months ago, I started noticing the shift from AC/vent to defrost under acceleration far more frequently, but then it rolled back to the vents, now it's just stuck on defrost.
I've owned the truck for about 14 months (bought in April of 2017). First summer, little issue (happened a couple times, didn't think much of it). Winter, left it on defrost. When things started warming up 2-3 months ago, I started noticing the shift from AC/vent to defrost under acceleration far more frequently, but then it rolled back to the vents, now it's just stuck on defrost.
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Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
Typically, when you only have defrost, this is either a vacuum, or blend door actuator problem.
If the symptom is variable (or progressed from that way) based on throttle setting, then it is absolutely a vacuum issue. Gasoline engines do not have an electric vacuum pump, the engine supplies the vacuum.
Senior User
Joined: Feb 2010
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[QUOTE=projectSHO89;18029898]This is NEVER a blend door problem, it is USUALLY a vacuum issue.
I had this issue on a Crown Victoria, where it was a blend door actuator, so just assumed, that could be a possible culprit, if it wasn't vacuum related. Thanks for the clarification.
I had this issue on a Crown Victoria, where it was a blend door actuator, so just assumed, that could be a possible culprit, if it wasn't vacuum related. Thanks for the clarification.
Hotshot
Joined: Jan 2004
Posts: 19,768
Likes: 1,082
From: St Louis
The "blend door actuator" is for temperature control. There are other actuators and doors that control airflow inlet and outlet selection but they are not called "blend doors", they're generally called "mode" doors.
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