[Lilloccgirl]

Looking over some of the tubing in my 04 blazer and noticed that this wasn't going to anything does anyone happen to know what this is and what it's supposed to connect to?

 

[aitch]

I can't really help positively ID the hose function - are there nearby hoses that aren't connected? Windshield squirter nozzles? One thing for sure, the vacuum hoses below thew wire harness are in need of replacement.

 

[Life is a Enigma]

I have a 04 2dr Blazer mine don't have that hose. Let's start what is it hooked up to? we see where it ends. That might help figure out what it went to. Your other vacuum line in the picture is in desperate need a replacement looks like it's getting ready to disintegrate.

 

[oldeerslayer]

If you have the 4 button AutoTrac 4wd switch that would go to the front axle vacuum switch on the firewall. The Tee should be connected into the rotten hose.
This is how your vacuum lines should look and the 2nd pic is of the front axle engagement switch on the firewall.

Another angle