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by glenny08 on November 20th, 2006

glenny08

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I have a 2000 Jeep Cherokee and the only place the heater fan will blow air is through the windshield vent. If I switch to any of the other locations on the control nothing happens. What's wrong?

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Answers. 5 helpful answers below.

  • by DenLorsTools on September 29th, 2007

    DenLorsTools

    If your Jeep has manual air - not dual zone this problem could be caused by a vacuum line broken or cracked. With engine running, open the hood and check the vacuum line near the ac lines that go through the firewall follow it back to the intake manifold while listening for a whistling sound if the vacuum line has any leaks this will cause the ac to blow through the defrost vents.

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  • by cgallen on July 30th, 2008

    cgallen

    The door that controls flow between defrost/vent/floor is referred to as the "mode door". This door is vacuum controlled and the procedures listed in earlier answers are a good starting point. In the grand cherokee, the vacuum actuator motor is located under the driver's side dash, above the transmission tunnel. If you get in the right position, you can see/feel the vacuum motor and the connecting rod that goes up to the door. You should be able to see this move when you change mode.

    One other thing to check and this will sound weird. The cruise control system is also dependent on engine vacuum. If cruise control is broken, this is almost a definitive diagnosis of a vacuum leak. Usually the leak is a loose or rotted vacuum line under the hood. You also want to look at the check valve(one way valve to hold vacuum under different engine speeds). You can trace a vacuum leak just like looking for an electric short with a hand vacuum gauge/pump. Just trace back from the actuator motor until you find the leak. Sometimes you can borrow one from the big parts stores under their tool lending program, or Harbor Freight has a decent one for around 30 bucks.
    Feel free to contact us through the web site at www.heatertreater.net if you have additional questions.

    cgallen

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  • by UGoLeftillGoRite on October 4th, 2007

    UGoLeftillGoRite

    9 times out of 10 it is a vacuum line running to or from your vacuum resevoir which provides power to the "air motors" that control the ducts in your system. There is no servo to speak of, the knob that controls this is just redirects that vacuum power to the respective motors to open and close the vents. By default if it loses suction it will revert to the windshield vent for safety purposes (defrosting ice and condesation). Check your lines running from the reservoir to your firewall for cracks or leaks.

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  • by geek860 on November 26th, 2006

    geek860

    You must realize that having it stuck on the windshield is the best possible position. Better than being stuck on Floor only...

    Regardless, however, in my 2000 Intrepid the air flow knob controls a servo that directs air flow. (If I listen closely I can hear it whirr when I change it) Given that you have the same model year and manufacturer, I'd guess that this servo may be broken. I'm no expert on HVAC systems so this is only an educated guess, but get the mechanics to check this first when you take it in. If they find it's the servo you could save labour costs (you don't need to pay them to find the problem.)

    Whatever you do, it will need to be taken into a shop. The dealer's probably best for this kind of thing.

    Good Luck,
    Hope this helps


    *To stewgots:
    I have an intrepid ES. It's the luxury model so to speak. Whenever I change the air direction (windshield, floor, etc) or turn off the air, I can hear a distinct 'wirr' noise. I have been around cars for a long time and know that this must be a servo or similar. My guess is that they are made to last the life of the car and therefore only a mechanic would be able to replace them. I don't think it is in the engine bay, since that would not make it easy to hear. It is probably under the dash, behind the firewall and directly connected to the HVAC system. Call your dealer and see if they know. A servo being there is an educated guess, but then again I don't build cars...

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  • by jamesscottforbes on May 30th, 2012

    jamesscottforbes

    I had the same issue with my 2004 grand jeep cherokee. The A/C would only blow on the winsdhield and sure enough the cruise was also broken. I found the 90 degree vacuum tube by the engine block was loose - I pressed it back on and both worked. Free repair ! YEAH !!!

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