Question about 2000 Dodge Ram 1500 Truck

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I have a 2004 dodge ram pickup. The a/c will not switch from the floor to the dash vents. Where are the vacuum line that I should check and how do i get to them

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  • viperco Apr 07, 2011

    I* did not find the black hose. As it turns out the air is moving from the vent to the floor, but there is not much air coming out. it is making as much noise but less than half of the usual amount of air is coming out, even on the highest blower setting. theblower makes more noise, but the amount of air is not right



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  • Dodge Master
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The System is operated by vacuum motors, the vacuum source is a black plastic vacuum line that comes from the engine bay on the passenger side. Go under the hood and at the firewall locate that black plastic line, follow it along to the plastic vacuum storage tank that holds the vacuum for the AC/Heater control head, pull the line off the storage tank you should hear a loud hissing noise as the vacuum leaks out, if you don't have any vacuum at that tank follow the other line attached to that storage tank it will go to the engine, the system gets its vacuum supply from the intake manifold in the back area, the hose connect to what we call "Vacuum Tree" look for any leaking or damaged/disconnected hoses. If you do have vacuum at the tank then check inside the truck under the dash where the vacuum line comes through the firewall, it may be pinched off, follow that line it goes to the back of the dash control, make sure you have vacuum there. These are all the common reasons for the no function control of the air discharge I have found in my 35 years of wrenching.

Posted on Apr 07, 2011

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  • yadayada
    yadayada Apr 07, 2011

    Pull the panel under the dash off on the passenger side and look under the dash for plastic vacuum hoses, they are there, the vacuum supply line is black and about the size of a cheap ink pen refill cartridge. The whole system is operated off vacuum from the engine. Did you look on the engine to see if you can spot the hose?? Back of intake.

  • yadayada
    yadayada Apr 07, 2011

    OK I got it wrong, the door are moved by electric motors in the 2002-2008 Rams , the motors have enough power to break the plastic doors that divert air and control outlet temperature with in the duct work of the system. There is a company that makes kits to repair all the problems these system have, they come with full instructions. I will tell you that you have a broken "Mode" control door, to repair this requires the entire dash be removed. Please read through the entire article but here is the important part that really pertains to your problem. Here is the web link to the comapny that makes the kits.

    Mode Door 1.

    a. This door regulates air flow to either the dash vents or defrost/floor. If you have air flowing only through the vents with no defrost or floor, this door is failing. From our experience, this door is usually the first domino to fail. Not sure why, just is.


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