heater blows thru defroster only

I saw a post relating to this and this tech. service bulletin link was helpful:
http://home.sc.rr.com/janet/TSB/24-01-96A.htm

MY QUESTION: My heater will only blow thru the defroster, no matter what position the switch is in, and no matter whether I am accelerating or idling. I think (HOPE) it is just a vacuum hose problem. Where can I find the vaccuum hose that runs to the dashboard? How can I be sure it is a vacuum problem and not the "mode vacuum motor" as described in the TSB link above? I could go out there and fumble around for an hour freezing my fingers off, but I thought maybe someone knows exactly where to find the vacuum line.

1993 Jeep GC, v-8, AC,

JERRY

There is a diagram in that service bulletin that shows it is located at the back of the engine on the passenger side.

I'm not sure the exact vacuum fitting on the engine but it is on the passenger side under the throttle linkage .

JD

Sorry I didn't get notice of a reply to my post... I FIXED IT! It was a vacuum hose that was rotted at the end. I trimmed it and remade the connection, and presto! It was fast and easy... The vacuum hose is just as Pascal described...passenger side, close to firewall. Shares vaccuum with a line that runs along the back and along the riders side of engine compartment. Sorry no pix.