The vacuum assist pump in the right rear fender of my 96 c280 is continuously cycling every 15 seconds or so when the air fan is on (a/c can be on or not, doesn't matter).

I've read the posts and checked the vacuum manifold by the front right fender near the firewall in the engine bay. The connections and the manifold looked ok. I then disconnected from there what I determined was the vacuum line to the vent controls under the glove box. This stopped the cycling of the pump. This just added support that the problem lies beyond the vacuum manifold in the engine bay and somewhere along the green line or in the vacuum control unit for the vents under the glovebox.

I took out the glovebox and under dash panel to examine the vacuum control unit and it, too, looks good with no apparent leaks. I should say that all the vents are working and I can see some of them working with the glove box out. I've disconnected the line to the vacuum actuators for the center vents and felt what I thought was good suction. My question at this point is:

The vacuum control unit by the glove box which controls the opening and closing of the vents looks like it's specifically made to be tamper proof. It seems this is where I should test the vacuum and vacuum lines going to all the actuators. How do you unplug the lines coming out of this control unit?

Also, how do you get access to the vacuum storage tank in a C280 mentioned in some of the posts? What does it look like and which vacuum lines is it connected to?