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Thread: A/C issue

  1. #1
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    Question A/C issue

    A/C will go into windshield defrost mode with half throttle or greater. The only way to get it back out of the vents is to turn off the climate control and turn it back on with feet off of all petals.

    Already changed the box in the firewall behind the passenger side head. A/C is cool, but not cold... probably needs a recharge.

    Any idea on what is causing this defrost mode with throttle usage?

    Thanks!
    "Bye Bye, Johnny B. Goode."

  2. #2
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    Quote Originally Posted by Motorhead350 View Post
    A/C will go into windshield defrost mode with half throttle or greater. The only way to get it back out of the vents is to turn off the climate control and turn it back on with feet off of all petals.

    Already changed the box in the firewall behind the passenger side head. A/C is cool, but not cold... probably needs a recharge.

    Any idea on what is causing this defrost mode with throttle usage?

    Thanks!
    Sounds like a vacuum leak. As the engine speeds up you get less vacuum.

    Low vacuum makes the system go into fail-safe mode - heat & defrost.

    If the o-rings (might be the source of the vacuum leak) in the EATC haven't been replaced, I can do that for you.
    “When you can’t make them see the light, make them feel the heat.”
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    "The only way to deal with the Islamic State - these blood thirsty, blood-drunken, terrorists -
    is to kill them, keep on killing them, until you kill the last one, then you kill his pet goat."

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    “Be polite, be professional, but have a plan to kill everybody you meet.”
    "I come in peace. I didn't bring artillery. But I'm pleading with you, with tears in my eyes, if you **** with me, I'll kill you all"
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  3. #3
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    +1 vacuum leak.


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  4. #4
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    Check all the vacuum hoses in the engine compartment. As these cars get older the hose get brittle and break off. Also check the vacuum tank on the top of the drivers side fender (black square box under the hood).
    “When you can’t make them see the light, make them feel the heat.”
    Ronald Regan

    "The only way to deal with the Islamic State - these blood thirsty, blood-drunken, terrorists -
    is to kill them, keep on killing them, until you kill the last one, then you kill his pet goat."

    Lt. Colonel Ralph Peters

    “Be polite, be professional, but have a plan to kill everybody you meet.”
    "I come in peace. I didn't bring artillery. But I'm pleading with you, with tears in my eyes, if you **** with me, I'll kill you all"
    General James Mattis




  5. #5
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    + 2, vacuum is leaking somewhere as engine has less vacuum when throttle is open versus throttle closed. It is likely the usual spot, the EATC unit.
    2004 SB #2150 of 3214 Moonroof, Heated Seats and 6 CD Changer. Non OEM Mufflers and 32,XXX miles and counting.

  6. #6
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    Is the EATC unit the box by the passenger side head in the firewall?

    I can give the O-rings another try.

    My van goes unto defrost mode on and off the throttle, but it doesn't need the A/C system shut off to go back out the vents.

    I will hunt under the hood for something disconnected or broken, but those O-rings might be the issue again hua?
    "Bye Bye, Johnny B. Goode."

  7. #7
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    Quote Originally Posted by Motorhead350 View Post
    Is the EATC unit the box by the passenger side head in the firewall?

    I can give the O-rings another try.

    My van goes unto defrost mode on and off the throttle, but it doesn't need the A/C system shut off to go back out the vents.

    I will hunt under the hood for something disconnected or broken, but those O-rings might be the issue again hua?
    It depends on what o-rings you used, was silicone dielectric grease used, who did it, etc......

    EATC - Electronic Automatic Temperature Control - it's the unit in the dash used to adjust the fan and HVAC settings.

    The box on the firewall is the BCM... whole different problem.
    “When you can’t make them see the light, make them feel the heat.”
    Ronald Regan

    "The only way to deal with the Islamic State - these blood thirsty, blood-drunken, terrorists -
    is to kill them, keep on killing them, until you kill the last one, then you kill his pet goat."

    Lt. Colonel Ralph Peters

    “Be polite, be professional, but have a plan to kill everybody you meet.”
    "I come in peace. I didn't bring artillery. But I'm pleading with you, with tears in my eyes, if you **** with me, I'll kill you all"
    General James Mattis




  8. #8
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    I used I rings sold at a ford dealership. It didn't quite fix the issue last year. I am thinking it's not the o rings and is another issue. I will search under the hood later as advised.
    "Bye Bye, Johnny B. Goode."

  9. #9
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    Quote Originally Posted by Motorhead350 View Post
    I used I rings sold at a ford dealership. It didn't quite fix the issue last year. I am thinking it's not the o rings and is another issue. I will search under the hood later as advised.
    So I gather they were not silicone o-rings......
    “When you can’t make them see the light, make them feel the heat.”
    Ronald Regan

    "The only way to deal with the Islamic State - these blood thirsty, blood-drunken, terrorists -
    is to kill them, keep on killing them, until you kill the last one, then you kill his pet goat."

    Lt. Colonel Ralph Peters

    “Be polite, be professional, but have a plan to kill everybody you meet.”
    "I come in peace. I didn't bring artillery. But I'm pleading with you, with tears in my eyes, if you **** with me, I'll kill you all"
    General James Mattis




  10. #10
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    Quote Originally Posted by fastblackmerc View Post
    So I gather they were not silicone o-rings......
    Pretty sure they were rubber. Which I am now understanding is the incorrect material. Yes?
    "Bye Bye, Johnny B. Goode."

  11. #11
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    Quote Originally Posted by Motorhead350 View Post
    Pretty sure they were rubber. Which I am now understanding is the incorrect material. Yes?
    Yes, I can fix it right for you...............
    “When you can’t make them see the light, make them feel the heat.”
    Ronald Regan

    "The only way to deal with the Islamic State - these blood thirsty, blood-drunken, terrorists -
    is to kill them, keep on killing them, until you kill the last one, then you kill his pet goat."

    Lt. Colonel Ralph Peters

    “Be polite, be professional, but have a plan to kill everybody you meet.”
    "I come in peace. I didn't bring artillery. But I'm pleading with you, with tears in my eyes, if you **** with me, I'll kill you all"
    General James Mattis




  12. #12
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    Quote Originally Posted by fastblackmerc View Post
    Yes, I can fix it right for you...............
    Does napa or any local auto store sell the proper material? I have done it before, but let's make sure the material is right this time.

    BTW PM me your address, it's about time I send you that Phil Spector DVD.
    "Bye Bye, Johnny B. Goode."

  13. #13
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    I put in Napa rings and nothing really changed.

    Upon starting the car, air came out the vents, but it was warm and I could not adjust where the air flow was coming from.

    I decided to drive the car.... like I do and things went back to the way they started.

    Cold air out the vents until half throttle or greater, then air goes out the defrost and will not come out the vents until I turn everything off and on again.

    I will check for vacuum leaks.... or does Napa not sell the correct O-rings?

    Thanks so far guys.
    "Bye Bye, Johnny B. Goode."

  14. #14
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    The EATC might be bad.

    I had my main vacuum line that runs from the check valve under the hood, and goes into the cabin by the gas pedal, literally melted shut and in two pieces. My car would just do defrost/floor period. So definitely sounds like a vacuum problem. As far as how cold the air is, do you know if the blend door is working fine? Do a self test in case there are some codes present.
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  15. #15
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    No codes on the car, but I will check out what you told me.

    Thank you.
    "Bye Bye, Johnny B. Goode."

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