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Old 07-30-2012, 04:16 PM
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Join Date: Jan 2011
Location: NC
Age: 33
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Vehicle: 2004 Dodge Ram 1500 4X4
Trim Level: Sport quad cab
Color: Bright Silver Metallic
Engine: 2003-2008 345ci (5.7L) Hemi V8 345hp 375lb/ft
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Originally Posted by ArtNJr View Post
I'm about 99% sure the system which switches the direction of the air coming from the fan (floor, defrost, etc.) is vacuum operated. There may be a vacuum line loose & even one with a pinhole leak in it will keep the system from working properly. A service manual will help you find where the lines are & how they should be routed. There's even one for the cruise control on my diesel truck & it's a bear to get to, under the driver's side battery!
It's a good thing you left that 1%, lol. The doors on our trucks are controlled by little electronic motors rather than vacuum controlled like most vehicles.
***EDIT*** This applies to the third gen trucks....I'm not sure about the pre-2002 trucks.

This is just a guess and it may not help a lot but my guess would be that your problem is not the HVAC doors. If it were, it would likely be mode door 2 instead of the blend door. The blend door controls the mixture of hot/cold. Mode door 1 diverts air from the main face vents to the secondary part of the system. Mode door 2 controls whether the air then goes down to the floor or up to the defrost. Typical failure of the doors occurs when the plastic limit pins or the plastic doors themself break from the pressure exerted by the electronic motors. Failure of mode door 2 typical results in the door falling down completely blocking the floor vents and diverting all air from this part of the system through the defrost. This is why I do not think your issue is mode door 2 or any HVAC door for that matter. I suppose it is possible that mode door 2 has stuck in the middle and is allowing air to go both ways but I find that unlikely, especially when considered with the other electrical problems you are having.

If you wish to troubleshoot the HVAC doors you can go to youtube and search "HeaterTreater Dodge Ram". I'm not sure they even offer a vid for mode door 2 though because it is very deep in the dash and is by far the hardest door to access.
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Last edited by starquestbd22; 07-30-2012 at 04:19 PM.
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