Not a newb. RENIX a/c?

ok, so i have had several xj's in my life, and only one of them has had working a/c before my current one, and it was because i replaced a bunch of parts.
the one i have now works, and blows nice and cold. it has been converted to r134a, and all is well in that department. my problem is that it will only blow through the defroster vents. i know that the controller and blend door are vacuum powered, so i pull the controller out, and with the engine running, i notice that i am getting no vacuum at any of the little ports/hoses on the back.
where is a good place to start looking to fix this? is the main vacuum line for the a/c any specific color? right now all my a/c can do is fog up the windshield and make me yell bad words at my jeep.
EDIT: this is a 1990 xj- 4x4, 4.0, aw4, dana30/35

Vaccum reservoir behind bumper on passenger side. Look there for disconnected hose or something. Also, the hose to the reservoir runs under the battery box...common place to develop a leak. Also, make sure the vaccum source (intake manifold) is connected and operating correctly.

The lack of vaccum not only affects the AC, but heater will also only blow out defrosters.

X2^^

check where that football/softball-looking-thing ended-up when the new bumper went on. My guess is that it either got tossed, or moved.

If it was tossed, replace it. If moved, inspect the vacuum line to it ( it usually breaks around the battery)

There are two vac lines coming out of the firewall just to the right of the heater core hoses, looking at engine from front. A black line and a pink or tan line thru a single grommet. The black one goes to the vacuum resrvoir, it can get brittle and has the dubious path under the battery tray. Those usually get nasty, can crack, break, corrode, etc. That's the first suspect.

Then look at the pink/tan line to see if it's connected to the heater valve, cracked or broken. Vac line is super cheap in bulk, a foot at a time. Replace any messed up lines.

If you're in doubt about where a leak could be blow some smoke (like a cheap cigar)into any end and see if it comes out in an unexpected spot.

thanks guys! now i at least have some places to look! i'm about to go wheeling, so i'll just let the windows down and mess with this stuff on my next day off. i'm not too worried about a/c when i'm in the woods....