2004 Ford Crown Victoria LX, 4.6, AC Not Blowing Correctly (Air Blowing Erratically)

***This is not the actual vehicle. This picture can be found here: http://photos4.automanager.com/022534/912caaf73c96ba49b30cbfdde96d29fb/666df77415_640.jpg.***

We had a 2004 Ford Crown Victoria LX with a 4.6 come into the shop with a customer concern of the AC not blowing correctly. Upon further investigation, we found the AC, when in the Norm AC or Automatic AC position, would sometimes blow the air out of the defrost and floor, instead of the vents.

Additionally, when driving the vehicle, at about 45 MPH, the air would switch from the vents to defrost/floor and then, once you decelerated, back to vents. Once it switched back, it seemed to stay there.

After checking the OE info, I checked several components and hoses to make sure everything was okay. Everything under the hood checked good. 

I then turned my focus to the passenger compartment. I never follow the OE "diag tree" for these, because I find there are a lot of unnecessary steps to it. 

The first thing I did, was disconnect the vacuum connector under the passenger's dash to make sure vacuum was there (sorry no picture of this). It was. I next went to the Climate Control Module in the dash.

I removed the four fasteners holding it in place, so I could pull it out and look at the back side of it.

 Below is the unit removed from its mounting spot. (Notice the different colored vacuum lines going to the unit.)

I then disconnected the vacuum connector on the rear of the CCM (Climate Control Module). There are two fastener nuts to remove to be able to do this.

Here is a look at the vacuum connector:

Next, I connected a handheld vacuum pump to the port with the black plastic line. The black plastic line is the source vacuum for this unit (it comes from the intake manifold). I wanted to be sure we had source vacuum to the unit before going any further. See picture below for the hookup:

The other vacuum lines go to various HVAC doors. The blue, for instance, goes to the door controlling air flow to the vents. Three of these can be seen through the hole where the CCM was removed.

You can see in the above pic three of the lines: the blue, the red and, just to the bottom (on the same one the red is connected to) is the yellow. 

Now, I was ready to once again drive it down the road. This time I had the vacuum pump/gauge installed to keep an eye on the vacuum as we hit our 45 MPH mark.

Below is a picture of the gauge reading our source vacuum, which was good, steady and constant at all times (at idle and any MPH/load): this told us, there was no issue with it. 

You can see from above, it was reading about 17 inHg. This is more than enough vacuum: so again, this checked out good.

We then moved to the port with the blue vacuum line (for the vents). As we drove down the road, we kept a close eye on the gauge. As we hit 45 MPH the vacuum dropped significantly (it should hold steady at all times). See the pic below:

Below is yet another picture, this time the vacuum is a bit more, but still significantly low:

This verified an issue with the CCM. There is a vacuum unit internal to the CCM which is designed to hold the source vacuum. It was failing. We opted to replace the CCM. 

In the picture below, you can see the vacuum holding (on the port with the blue line: the one going to the vents) as it should.

We put it all back together and drove it several more times. Each time it worked as designed. We made sure all the controls on the new CCM functioned properly and shipped it.