2000 Dodge Ram heater/defroster air direction selector

I have found another website while waiting for answers from you. In it it discusses a "blend door" problem that happens to Dodge trucks of my year. It also shows a fix. Would you tell me if this could be the problem and the solution. Please look at heatertreater. Net and look at the 98-02 Dodge Ram. The video shows what I believe to be the piece under the dash on the heater component covers. (Redid the reply so hopefully you can have a link).

It didn't redo. The link is heater treat. Net

I'm not having trouble with the temp changing as I change the knob. I didn't understand that that was what the blend door did. When I unscrewed the controls (3 of them, the temp, the fan, the direction of air flow) I couldn't pull the controls far out. The wires won't allow much leeway. How do I check the vacuum? I have no tool to check it if I find it. Where is it? How do you unfasten it? Would I be able to determine if it's working correctly by just covering the hole and seeing if there is a vacuum?

I could barely see the diagram but I think I can find #3. I'll also see if I can find a vacuum tester. How do I unplug the line to test it? Does it just pull out? Do I have to take the entire unit off the switch and test it without disassembling the unit? I'm sorry if it appears I don't know much about what I'm doing, but I don't.

While waiting for a reply I looked up the vacuum diagram on line and found it in the truck. I noted that there was a one-way valve, with two rubber connectors attached on either end to tubes. The rubber had deteriorated and had breaks in it. I replaced them and, for a little, I had control of where the air came out in the truck. Then it stopped. I went to AutoZone and while they have that tool you talked about, it only produces suction. They didn't have anything to measure suction. I do have suction at the intake side of the one-way valve. I thought I should see if at the knob there is suction. I'll try to disconnect the unit with the 3 knobs so that I can isolate the suction line and determine if there's suction there. Does that sound correct?

I'm sorry it took so long to reply. We had to go out of town. Today I went back to work. I used your information to proceed. I took the switch out of the dash, disconnected all the plug-ins, and then took the vacuum switch apart. Actually, I just separated the plugged in portion. I turned on the ignition and started the engine. There didn't appear to be any vacuum in any line, even the black one. Then I turned off the engine and followed all the black tubes and found one that went through the dash. I was going to unplug it, but then while seeing where to best take it apart at, I noted a break in the line. I taped it with electrician's tape, started the truck, and everything worked. So there was the problem. It's now solved. It took some time but it's done for no other cost than time and my donation to you. Thank you for all your help. You made a great difference in me solving this or not.
Frank