Should there be airflow with AC on "O?"
 

87 300E I get airflow from side vent with climate control button "O" pushed. Is this normal function?
Which vac control units go with which number on the maniforld behind the glove box?

No, the O button means OFF...

That would mean that the fresh air vacuum element isn't closing completely.

Thanks for the data. I have asked >10 people with conflicting results.
Now
Is the fresh air flap the one just behind the blower motor? If so can I fix it from the engine side? When I change the blower motor I noted foam on it was old and crumbly so I vacuumed the foam off so it would not fall into the AC airflow. The flap also would swing freely. If I open the passenger door quickly I hear the flap clank and if I close the door quickly I see leaves on the air intake jump.
If I cannot fix it from the front, which number(from the manifold box behind the glovebox) controls it?
Thank you for knowing the answer.

This is the vacuum diagram... hard to get good scan at 65K max size!!!

Thank you for your help.
Is this for an 87 300E? My V7 Switchover valve unit(I called it a manifold) has only 6 numbered outlets top to bottom.
It also looks like there are two fresh air diaphrams(#42) and I think I only see one diaphram when I took out the glove box(likely #38 or # 42) so I will have to pull the dash if this vacuum function diaphram is correct?

The vacuum diaphram is correct. My memory was not.
 

I must have had Alzheimers. I pulled the glove box, recounted and found there are SEVEN numbered lines coming out the side and one out the top. The colors of the vacuum lines are correct too. Now I will put a vacuum on the fresh air lines( 1 and 2 )