As the summer is here and things are starting to heat up I figured I'd investigate as to why my AC has started blowing out the defrost, and floor vents, but won't switch to the front vents.
Now I know by default if the programmer is not receiving vacuum it will default to this, so I decided to try to figure out where it was not getting vacuum , if that is indeed the problem.
I disconnected the purple hose where it connects to the black one, and started the car, and verified there is vacuum, I do not have a gauge to tell if it is sufficient, but I do not it feels fairly strong.

Let me include the link that I used to assist me.
A/C Service Tech Tip: How to redirect the cooled air in late model GM cars

With that article I see they got one thing wrong, the nut going to the vacuum connector on the programmer is 7mm, and not 8mm.
Below is a picture of what I am having a problem removing.


I got this nut off and for the life of me could not figure out how to "easily" remove this connector, it refused to come off easily though, and I am afraid of breaking it if I am too forceful.
Does just the clear part that you can see with the hoses on it come off of there, or does the small black part surrounding the connector come off with it?

See this next picture, it is an opened up programmer, looking at this it looks like the black part in question is still attached to the programmer, so am am guessing carefully wiggling the clear connector with hoses on it until it comes off is how you do it.
Anybody know for sure?


Never mind, I just noticed in pic 4 that it appears only the clear part of the connector comes off, the black part stays attached to the programmer.


I guess I'll try again to remove it later on when it is a bit cooler, it is a pain in the back to lay down and loop up in there at it..
If anybody has any suggestions as how to easier remove the connector let me know.
Also if anybody has info on how to remove the whole programmer I could use it, as I have a feeling if I am ever going to fix whatever the problem is I am going to have to remove it, and most likely get some 1/8-inch vacuum hose to repair the existing programmer, as that is the only method most likely suited to my current budget.

I know I should verify vacuum pressure first to see how much vacuum I have, but I am fairly sure the vacuum is fine, as I do have it, I replaced ever soft hose connected to anything vacuum related recently.

If and when I do find the issue, and repair it, I will be sure to get some pictures, that way others do not have the same questions as I have right now.

Did some searching on my own, came up with some info on removing the programmer.

1. Open the glove compartment, disengage the stops and swing the door down.
2. Detach the electrical and vacuum connectors.
3. Remove the driver temperature valve link rod.
4. Unfasten the screws and remove the programmer from the vehicle.

Attaching pic that shows how to remove it, seems easy enough, as long as I can remove the vacuum connector.
That and if I can figure out how you remove the driver temperature valve link rod.
I'll look at it tomorrow and see if I can figure it out.
I hope I do not have to remove the screws labelled 3, as by the looks of it they are on top of that part that has the driver temperature valve link rod, and I am not sure how I would get to those, unless my whole dash was removed.

Question, is the vacuum problem with the programmer the only thing that can keep it from changing to the front vents?
If there is something easier to check first, or something I should check before trying to remove the programmer, then that is what I want to do.

Editing to add a pic of a progammer, it looks like I can see a hole where #8 in the diagram is at, but there are two holes, and only one screw shown in the diagram as number 8, maybe the other is just held on with a plastic clip or something.

Unfortunately Wm, you are correct...you remove that nut, and sometimes when you try to remove the vac harness, it won't come off.....you yank and you break the "nipples" the vac harness attaches to....impossible to glue back on, even if you can get them out of the harness in one piece...

with a coupling, and a long piece of vac line, attach it to your source and then remove a line from the actuator and attach the extension to the actuator...if it moves, you know you have sufficient vac....

You really need a diagnostic tree, to know if the problem is the control head or the programmer.....parts are too expensive to guess...

That is my main fear, some of the nipples breaking when I pull the connector off, I tried to think of something that may help keep that from happening, but all I could think of was maybe carefully using a hair dryer on low heat, held far enough away not to melt anything, I think that may make them less likely to break off a nipple, but still almost anything I do the first time Murphy'* Law comes into play.
I really wish I had more info on how to properly diagnose the problem, but I don't have any of the FSM'* for my car, I plan to get them once I can afford to, but money never seems to be in an abundance anymore.
I thought about the control head maybe being the problem, as I can see the vac lines run towards it, so I assume they run inside of it as well as the programmer.

Parts are expensive for sure, and it seems there are not many programmers for sale, I seen two on e-bay, like 350.00 to 400.00

I guess I'll wait till I can get some coupling for 1/8" vac line, and some 1/8" vac line before I try to remove the connector to the programmer, and the programmer.
Then I could attach the vac line to the black source line, the one that connects to the purple vac line, then I could try to detach individual lines from inside the programmer, and see if I can get the air to switch off of the defrost/floor, I just wish I knew which source each of the 4 lines inside the programmer go to.

Thanks for the response Gus!

I clicked on your article that describes the repair....very good article....shows how you can eliminate the nipples and harness by individually connecting each colored vac line directly with vac lines and couplings....

Basically with the state you are in, either the defrost -A/C actuator is bad, or it is not getting vacuum........here is another thing you can do.....get a long piece of vacuum line, disconnect the defrost actuator(it will have a yellow line going to it).....now attach the long vac line....turn on your system...command max A/C.....now suck like you've never sucked before, on that vac line, OR, just attach a vac pump and start pumping(should hold unless the vac pump is leaking or the vac actuator is leaking......you should now get air out of your vents,....if air comes out of your vents AND floor, this means you are not getting vac to the bi level actuator, either.....

As far as colors go, vac to the yellow line, allows air flow through the vents....no vac, sends it to the w/*...

vac to the red line will force flow to the floor.....vac to the blue line will cut off flow to the floor and allow flow just to the vents....no vac to either, will allow flow to vent AND floor......you can't have vac to both red and blue at the same time....

Vac to the orange line, will shut off outside air, and recirculate the inside air(also increase air flow)....