PeachParts Mercedes-Benz Forum - View Single Post

kerry · #3 10-19-2002, 01:41 PM

Update on the problem:
I tested the vacuum at the switchover valve. It is fine and pulls about 10 inches of vacuum. When I hook the line up to the center vent and T into it to test the vacuum, I can pull a vacuum and open the center vents. However, when the ACC operates, what happens is that the vacuum increases up the word 'Zero' on the scale on the Mighty VAc. When it reaches the 'o' on zero it stops and does not open the vents. If I give it a few pumps on the might vac up to 1 or 2, then it increases up to 10 on its own and opens the vents. If I release that vacuum thru the mighty vac back down to 1 it will build up again and work fine. If I hold the release until it goes all the way back to 'z' on zero and hold it there for a second, the same problem arises. It will only go back up to 'o' on zero until I give it some help with a couple of pumps.

If I disconnect the line from the actuator, and test the line, it works fine. If I kink the line to the actuator, let it build up a lot of vacuum and then let it go, the actuator will function on its own.

So, with a small amount of vacuum in the line, the actuator seems to be leaking. My increasing the amount of vacuum or pushing in the actuator about a quarter of an inch, the leak stops and the actuator holds vacuum until it is completely deactivated.

Can someone familiar with the inside of these actuators speculate about what might be causing the leak when the actuator is fully at rest? And further, what has to be done to rebuild them? It looks like the back has to be removed by releasing the three plastic catches. Can this be done in place? If so, has someone done it by feel on the center vent actuator without removing the bottom half and the actuating rod? It seems as though that would be the easier method compared to removing the dash.