No air out of cabin vents

[mario 3]

'87 300TDT replaced 5 of the vacuum pods thinking it may be the reason for no air coming out of vents after 45 minutes of running. the first 45 minutes or so everything works fine heating and cooling. After 45 minutes or so the vents close and the blower goes into the high mode but nothing comes out of any of the vents. Any info would be of help. Mario 3

[BrierS]

Mario 3,
From your description, you are using the center (auto) of the fan speed buttons . . . if you remove the glove box (2 screws holding the upper stationary latch plate and gently pop the two curved plastic pieces up-wards to allow removal of the inner box, you will find two pieces of importance. One, to the far right as you reach through the glove box opening, just under the side vent hose, the sampler motor/fan unit should be clipped in. Remove that and make certain it is working correctly/efficiently. The popular test is to see if a single ply tissue will be held to the small grill that is located to the left of your courtesy light console. This is of course with the motor/fan running. If that is working properly you have just eliminated one possible contributor. Again viewing through the glove box cavity, you should see the switching device where vacuum lines are attached leading to each of the vent functions. Testing the vacuum source there is where I started and then I used the miti-vac to apply slight pressure to each line to see if they would hold. From your description, you may be far ahead of anything I have offered. The third item I believe Larry Bible had written about was a hose under the dash that is supposed to have insulation on it. Though my memory is weak, it seems not having the insulation caused a problem with the system thinking it has achieved a certain temperature when it had not. Again, you have probably performed searches and read up on these items. Regardless, I'll be interested in following this thread since I have had my share of ACC woes.
Steve