Okay I am a newbie obliviously! I browsed through the first 3 pages, and found the answer sort of.
My AC blower was funky. It would only blow on 2,3,4, 1and 5 were dead! So i went to the Junk yard and got a new hvac control panel, did the same thing, so I returned it. Read up, and found out it's a relay, snatched one up for $22bucks at work. Dropped it in, and the fan works on all 5 speeds,so thanks!
BUT the vent selector does not work it seems to blow on defrost only! So what would cause this?

I have had this truck 1 month and this is the fist problem.

Oh to list the things I have done,
1)JET programed
2) Sylvania Silver Stars ultra hi and low beams
3)blower motor resistor
4)MagnaFlow (sitting on the couch)
5)MagnaFlow tip (also on the couch)

 

Feel behind the glove compartment or under it. There is sometimes a vacum hose that will come loose and allow the vent or defroster to switch. If not then look around the intake for a loose vacum hose.

 

ok, under the hood is there a specific side as where to look for a loose vacuum line?

 

There is also on some years (I am not sure what year yours is) a motor that switches the air from blowing from the different locations. It is towards the middle under the dash but a bit more on the drivers side. It will have a plug with a few wires going to it and a couple of metal bars that open and close the different locations of air flow. If one of the bars has come out or the motor is bad it will only blow out of the defroster. The best way to find it is look under the drivers side of the dash and reach up and move the vent selector switch and you will see a small motor down there turning. It is only about 3 or 4 inches square and maybe 1 1/2 thick and mounted on the side of the large air plenum. Hope this helps!

 

Here is what it looks like...

 

I'm not familiar with your problem, but I thought I'd take this opportunity to welcome a fellow Michigander. It says you are from up in Traverse City, I've spent quite a lot of time up there. I presently live in Ada, which is just outside of Grand Rapids

 

Thanks for the Welcome!
MY Sierra is a 2003.
I looked for a loose line and could not find any. Any other ideas?

 

Did you look for the motor under the dash? Also on the newer truck I have had to replace a few control heads. Try to disconnect your battery and reconnect it and see if it works temporarily.

 

okay I do not see the motor thing under the dash. I will disconnect the batter in the morning.
When I thought the hvac controller was bad i bought a used one and it did the same thing. then I found this board and found out it was the 22dolar resistor . in the back of the unit theres just 1 plug in right? may be i did not plug something back in.

 

So I went to the dealer today and spent $232 for a new mode actuator! They also told me that my #5 speed does not work (duh) because the pig tale is fried! that was $380 to have repaired. I declined I am hitting up the bone yard this weekend. I tried getting it at work but it's a dealer only item.

Oh so has any one replaced the pig tail? any tips or tricks?