I have a '99 Dodge Ram 1500 Van. The heat/air selecter moves from position to position but it only throws it to the windshield (defrost) and to half defrost and floor.

Nothing happens when you move it to the other positions. It just stays on the windshield or winshield/floor.

There must be a vacuumn control unit somewhere under the dash that controls this switching. What is the part called I'm looking for?

How do I get to it to replace it and where is the best place to buy a replacement part?

Please give me a step by step instructions to replace this unit if that is the problem.

Thanks in advance to all helps.

 

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You are the man!!!! Thank you......works fine!!!!

 

Thought my problem was solved.........BUT.....Took it on a trip today and it does the same thing. There is nothing wrong with the *****.

If you have it on Max Air....It will operate for a while coming out the dash vents and all the others. Than.....As if it has a mind of its own, it goes to windshield and floor.

Sometimes....If you leave it on Max, it will come back to the dash vents and all the rest and operate OK for a while. Than.........BAMM it quits coming out all the vents and goes back to the windhield, or windshield/floor.

Sounds to me like a bad valve (vacuumn???). I really don't know how these things switch when you move the **** to different positions.

All suggestion....Part name, Part number of defective valve and where is it and how do I replace it?

Please help if you can~~~~~~~~~~~~Ron

 

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Took it out for a trip today with the **** set on dash vents and discovered that cruising down the highway at a steady speed it works fine. Accelerate a little and it switches back to the floor. Let off the throttle and it switches back to the dash vents.

Tried it many times and it does the same thing everytime. I was going to post what I found and assumed I had a vac leak somewhere and you had already posted that it might have a vac leak.

I'll start looking. How can one test for a vac leak? Is there something I can spray around the connection? I know some of the vac lines hook in with a multiple plug.

Don't want to spray anything on that will deteroiate the rubber.

Thanks for all your help!!!!!

 

Start by testing the check valve on the passenger side of the intake manifold. There is only one vacuum hose coming out so it's not hard to find. Remove the check valve (note it's installed direction first) then blow through it in both directions. Air should only be able to flow one way. If it flows both ways replace the check valve. If it only flows one way then follow that vacuum line until you find a leak.

 

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You definetly are the man!!!! Opened the hood, check valve in plain sight and the vac hose was broke off about 1" before the rubber hose that hooks to the check valve. Pulled out the broken piece....put the vac line into the rubber connection and YAHOO everything is working fine.

Thank you so much for your help!!!!!

 

Does anyone know of an accurate diagram for the vacuum lines inside the dash? my 94 heater/ac controls are not working. I found a disconnected vacuum lline, but I cannot figure out where it connects. It only blows to the defrost and it only blows warm.