HVAC Blows out forward vents then stops for a while

Looked but didn't find a thread that covers this.

2004 Safari, 8th # is "X", 150,000 miles, plain Jane, nothing fancy as far as options.

Astro/Safari has vents that blow toward the driver and passengers and also vents that blow out of the side of the dash at the side windows. My problem is that the vents that blow toward the driver and passengers stops blowing air, for no apparent reason. It is like a door behind them shuts and prevents air from coming out of them toward the driver and passengers. The side vents still blow air out of them toward the side windows though.

The blower still operates well on all speeds.

Sometimes it comes out at the driver and passenger and sometimes it won't. It was blowing at us for about 2 minutes then it would stop for about 1 minute, then resume and repeat the same cycle again and again. It has gotten worse. Now, it rarely blows through the vents at the driver and passenger, but still always blows out of the side vents (next to them) at the side toward the windows.

I've checked fuses and found none to be bad. In the winter that is not a problem because I usually have the foot and/or defrost vents selected for the heat. But, now that summer is here (in Texas) I'm sweating. The air coming out of the little side vents pointed at the side windows just doesn't cut it.

Anybody had a similar problem? And, what is the fix?

check the vacuum lines. small rubber hose about the size of a air hose for a fish tank. In my chevy it is on the pass side behind dash. and there is one under the hood. anyhow search for your car to know where they are. If loose or cracked they will do that. If it came off it will stop all together.

Thanks, I'll look first thing tomorrow in the daylight.

I guess I have to pull some stuff from under the dash to check out those vacuum lines. I did find one line under the hood next to something AC related that is in bad shape, can't tell if it is leaking or not but got my fingers all black. I'll replace it first and see what happens. With any luck, maybe that'll be it and I won't have to start digging under the dash.

Yes the one under the hood is HVAC if that is bad or leaking then the ac will not work on high settings. Does it work on low settings?

The vacuum purge solenoid is located on the drivers side intake just above the No. 1 cylinder. It sits upright with vacuum lines hooked up to it, that's where that line feeds into. Hope this helps.

On the 2003 chevy 1500 van I did the vac lines on, They where located on the passenger side just above where your feet would be at behind the dash. You could actually just lean over and see them now removal required. It actually surprised me that they left them out like that but if I remember correct the blower line for the high setting was red or pink and the second one is located under the hood where the other post i sent you before says.

Thanks FishFind. Today's Friday and I got the day off. I'll let you know how I do

Update, no update. Sick as a dog, with flu like symptoms. I will get to the vacuum lines as soon as I can.

Look at the line running horizontally across the front of the throttle body. I'll bet a quarter it is deteriorated in at least one place.

http://www.wwdsltd.com/files/NVanHVACVacLine.jpg

That's a big help. Thanks Blue Bowtie. I just went out and checked it. It is a thin hard line and right where I felt for it I found the line severed and almost broken in two. I traced it back to the black pastic box that is on the passenger side and see that it is attached into the black box by a plastic fitting that also has a larger rubber line going toward the firewall. The larger rubber line is also deteriorating also. What are these parts called and where does the small line mentioned in the picture above go, to the right of the throttle body looking at the picture?

You'll feel the other end behind the compressor- plugged into a vacuum port.
I use rubber hose to mend or replace plastic line- windshield washer hose works well.

That was it. Big smile on my face when the fan blew straight at me from the dash. Life will be good again. We've already had a couple of near 100 degree days. Can't wait to drive to work tomorrow....wait, what did I just say. Hmm, I must be happy. Thanks a lot for the quality diagnosis and advice.