I haven't a clue how to post a photo , so I'm just gonna drop this link. Hope I'm not breaking any rules.

http://m.ebay.com/itm/131422949477?_mwBanner=1

Is this, along with the lines, what I should replace to solve my issues? And when I do the lines, should, is there any in the cab that I need to check as well? If so, what's the best way to get to them?

Thanks again

 

they arent that complicated. Should look something like this

 

A check valve that is 'in-line' like the picture posted at ibsrv.net would require that the equipment(HVAC) operated would have access to the reservoir somewhere on the reservoir side of the check valve. IOW there would be a 'tee' or dual ports to the reservoir.

MFP073 a slow drift to defrost while at highway speed indicates there is a leak in the vacuum operated mode 'motor' or vacuum lines / connections. The check valve may be leaking, but it is likely the under dash lines leak also. The engine vacuum will be low, but there should be enough to maintain position. There's enough leakage that the mover does not maintain position. The control can also leak.

Ford'05 it seems to me that you have to check your check valve first, as it's the easiest and simplest thing to verify. If the check valve is totally gone, the minute you turn off the engine, the vacuum will be gone, and the mode switch will shift to defrost as the springs inside will move as there is no vacuum holding them back.

There might not be enough vacuum to test using human generated suction, so if you do not have a vacuum source, wait, test using engine vacuum. Turn it around, install backwards into the vacuum line leading to the manifold, start engine and see if there's suction on the 'wrong' end. If there is, it leaks.
tom

 

How did you come to believe your vapor recovery purge valve needs to be replaced???? Do you now have a trouble code for it that you didn't post, or did you find its leaking with a smoke test, or find it physically damaged?

 

This thread is becoming confusing as there are two problem posts that are about similar problems.
I did not look at the ebay posting but would venture the charcoal canister is routed directly to the tank and to the intake, and has not a lot to do with defrost mode selection, OTHER THAN if there was a HUGE manifold leak through the canister vent valve, then vacuum would be significantly reduced. To find out, plug the vacuum line from the canister to the intake. I guess.
tom

 

Might be time for a "Swisher Sweets" smoke test!!!! lol

 

I've had those sitting in the console for testing for a few days now. Still not entirely sure how to preform that test. Mainly because I haven't identified the line I need to. I'll spend some more time under the hood today while reading this info.

 

So I think I found the check valve. It's a really tiny little thing huh? I downloaded the IB app again after a few years to post a picture but it's still giving me error messages like it used to whenever I try to open the posts I need to.. So. I'm gonna look at changing that check valve this coming week. Today was my off day and I didn't get around to working on the truck. The lines that it runs with actually look pretty good, but I haven't smoked them yet. I'll do that after I push this reply button.

 

I did the smoke test. No leaks. I put the valve on back wards. No leaks. I'm stumped.

 

ford'05:I did the smoke test. No leaks.

What did you blow smoke into? The reservoir?

Given that your system does not hold vacuum at all, going to defrost immediately upon shutdown, I would be removing the gloveboI think) and finding the 'motor' that moves the mode flap. With the engine running at idle, you should be able to watch the 'motor' move the flap as you change from A/C to Defrost modes. If you do, listen for hiss of leaking vacuum, and if you don't hear it, remove the vacuum line to the motor, and attach a length of tubing, apply vacuum. Cover the end of the tubing and watch to see if the motor 'relaxes' and allows the mode flap to move to defrost. If so, you have a leaky motor diaphragm. The control switch looks like a 'maze' made of a flap of rubber, with grooves that connect this to that, allowing vacuum to go here and there depending on the mode chosen. Sometimes the rubber flap will leak past the edges of the maze. You may be able to take it apart, clean it and re-assemble and it will work after. I think it is lubed at the factory with a silica based grease which helps seal the edges. It may dry over time and leak.
A 'mighty vac' hand pump is useful for this kind of problem. About $30 at auto stores & harbor freight.
tom