i have no a/c or heat coming from my center vents. any ideas?

No heat is by design.

My understanding is the vent controls are vacuum operated. I do not know exactly where it is, but there is a vacuum line that came loose on mine and only the outside dash vents for a/c worked. After 30 minutes of tracing vacuum lines, a mechanic friend found it.

This feature confuses a lot of new owners. Unlike a lot of other cars, MBs do not push much air through the center vents.

So you don't fall asleep while enjoying your ride through the park Same as having to stop to change from Miles to kilometers whereas Toyota you push a button while on the fly.

My center vent on my e only blows cold air and it blast it in my face. The side vents blow very little air if any my left side is always cooler than my right sideanyone haveing the same problem

As mentioned, there are vacuum operated flaps which divert the air flow depending upon CC settings. There is actually a WIS test procedure to follow for determining which flaps are not working based on a series of settings and observations. It's pretty detailed and long.

Where can i find that ?Did you mean the a/c sytem diegnostic. Cuz I tried that and all i got was a flashing light on the vent button it would not let me input codes 1-8